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Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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May 16 2018

Intermittent Fasting for Women: What We Know Now

By Mark Sisson
570 Comments

Hungry woman on a diet waiting with an empty place, isolated in whiteThis is an updated version of a Dear Mark column from 2012. You can find the original version archived here. The below has been completely updated for 2018.

The blank slate hypothesis has fallen. Everyone comes into this world imbued with attributes, characteristics, and predilections that are uniquely theirs. We’re all humans, but we’re a diverse bunch, and that makes it interesting. And though it also makes giving cookie cutter health advice impossible, I just take that as an opportunity to stand out from the crowd and provide actionable advice that genuinely helps real people.

A perfect example is biological sex. Anyone who’s lived with the opposite sex, been married, or had kids of different sexes knows that males and females are different—on average.

There’s a ton of overlap, don’t get me wrong.

We all need fat, protein, and carbohydrates. We all have the same requirements for sustenance and wellness. We all breathe oxygen, get stronger and fitter when we work out, use the same neurotransmitters, and produce the same hormones. The biological basics are identical.

It’s the details that differ. And matter.

Take fasting.

Fasting As Hormetic Stressor and the Influence of Biological Sex

Men and women both need to enter a “fasted” state in order to burn body fat. This should go without saying, but regularly undergoing periods where you’re not inserting calories into your mouth is an absolute requirement for weight loss and basic health, no matter your sex.

These periods are called “fasted states,” and they begin as soon as you stop processing the energy from your meal. An “intermittent” fast is an extended period of not eating done for the express purpose of weight loss and other health benefits. 

By definition, a fast is a hormetic stressor—a stressful input (no food) that in the right dose triggers an adaptive response that makes us stronger and healthier. Fasting triggers Nrf2, the “hormetic pathway” also triggered by other hormetic stressors like exercise, polyphenols, and radiation. Nrf2 initiates a series of defensive and adaptive mechanisms that help you respond to the stress and buttress your body against future stressors. But with too large a dose, a hormetic stressor can become a plain old stressor—one that overwhelms our defenses and harms us.

Making matters more complicated, the size of a hormetic dose is relative. What’s hormetic for me might be stressful for you. Many different variables affect how much of a hormetic stressor a person can tolerate.

With fasting, perhaps the most important variable to consider is your biological sex.

This really does make intuitive sense.

Biology cares most about your fertility. Can you reproduce? Can you produce healthy offspring that survive to do the same? These things come first.

And from that perspective, a woman’s situation is more precarious than a man’s.

You have a finite number of eggs, or “chances.” Men have an almost infinite supply of sperm.

When you are preparing to get pregnant, your body needs extra nutrients to build up a reserve and “prime the pump.”

When you are pregnant, the growing baby needs a reliable and constant stream of nutrients for almost a year. After a man gets someone pregnant, his biological involvement with the growing baby is done. What or when he eats has no impact on the survival of the growing baby.

After you’ve given birth, the growing newborn needs breastmilk. To make that milk requires additional calories and extra doses of specific nutrients. Modern technology allows us to skip nursing and go straight to the bottle, but your body doesn’t “know” that.

It all points to women being more finely attuned to caloric deficits. For example, women’s levels of ghrelin, the hunger hormone, are quicker to rise after meals.

This isn’t just relevant for parents or parents-to-be. Even if you’re not interesting in getting pregnant and having kids, or you have children and aren’t planning on any more, the ability to do so is strongly connected to your health. Reproductive health is health. As far as your body’s concerned, having kids is the primary goal and you need to be ready to do it as long as you’re able.

Where does fasting come in?

Fasting is simulated starvation. Amidst the most critical junctures of the reproductive process, even a single skipped meal can register as trouble. The problem with intermittent fasting is that it’s not just a one time thing. It’s a regular occurrence. Depending on the schedule you follow, you might fast every day, every other day, or once or twice a week. To the mostly unconscious body whose primary concern is your fertility, that can be alarming.

What does this mean for women interested in intermittent fasting Unfortunately, there aren’t many studies examining this question in women. There are a few, and I’ll get to those. First, let’s move to animal research.

What Animal Studies Tell Us

In male rats:

No matter the duration or degree of nutritional stress, a male rat’s brain chemistry responds with similar changes. Nocturnal activity and cognition stay fairly stable, regardless of the intensity of the fast. If you push the fast long enough, males will get a little wonky and frantic, but overall they maintain pretty well. It’s like they’re equipped with the ability to handle nutritional stressors.

In female rats:

Any degree of nutritional stress (fasting or mere caloric restriction) causes increased wakefulness (during the day, when they normally sleep), better cognition (for finding food), hyper alertness, and more energy. In short, female rats become better at finding and acquiring food when they fast, as if their bodies aren’t as well-equipped to deal with the stress of going without food. They also become less fertile, while the males actually become hornier and more fertile (probably to account for the females’ plummeting fertility). Ovary size drops (bad for fertility), adrenal gland size increases (which in rats indicates exposure to chronic stress), and menstrual cycles begin to dysregulate in proportion to the degree of caloric restriction.

One recent study found that placing young rats of both sexes on an intermittent fasting schedule had negative effects on fertility. While the male rats had lower testosterone, the female rats stopped ovulating, had trouble sleeping, and experienced ovary shrinkage.

What Human Studies Tell Us

One study found that while IF improved insulin sensitivity in male subjects, female subjects saw no such improvement. In fact, the glucose tolerance of fasting women actually worsened. Another study examined the effect of alternate day fasting on blood lipids. Women’s HDL improved and their triglycerides remained stable; men’s HDL remained stable and their triglycerides decreased.

Later, both obese men and women dropped body fat, body weight, blood pressure, total cholesterol, LDL cholesterol, and triglyercides on a fasting regimen. These people were obese, however, and perimenopausal women were excluded from the study, so the results may not apply to leaner people or women in the perimenopausal window.

One study compared continual calorie restriction (lower calories a little bit every day) to intermittent calorie restriction (lower calories a lot every once in awhile, similar to fasting) in overweight and obese women. Both groups lost a similar amount of weight, but the intermittent restriction group lost significantly more lean body mass. As I’ve always said, the kind of weight loss we want isn’t “weight loss.” It’s fat loss and lean mass retention (or gain). 

In the only heretofore extant human study on fasting and chemotherapy, seven females (including a 44-year old woman who was likely premenopausal, given when menopause usually onsets, though it wasn’t explicitly stated) and three males found that IF improved their tolerance to and recovery from chemotherapy.

Takeaway: male and female (mostly middle-aged, though that’s the population that generally gets cancer and undergoes chemotherapy) chemotherapy patients appear to benefit equally from IF.

What About the Effects of Training While Fasted?

One study looked at healthy men and women doing moderate intensity morning cycling either fasted (overnight) or fed (ate breakfast). Although both men and women displayed greater increases in VO2 max and resting muscle glycogen concentration in response to fasted cycling training, only men showed greater skeletal muscle adaptations when fasted. Women had better muscle adaptations when fed.

Another study placed both fasting and fed overweight women on an interval training protocol for six weeks. Both groups improved body composition and oxidative capacity to an equal degree. Being fasted or fed had no effect.

It’s sad to say, but that’s about it for fasted training studies in women. The vast majority deal with men.

How About the Psychological Effects Of Fasting?

In women, a two day fast shifted nervous system activity toward sympathetic dominance. Even though their cognitive function was unaffected, they were stressed out. In men, a two day fast shifted nervous system in the other direction, toward parasympathetic dominance. They were well-rested and relaxed. Their blood pressure dropped. Their cognitive performance improved.

How About Autophagy?

One of the main benefits of intermittent fasting is an increase in autophagy, the process by which our body clears out cellular debris and repairs damaged cellular structures like mitochondria. A decrease in autophagy is usually linked to increased aging; an increase in autophagy tends to stave off the ravages of aging. Fasting-induced autophagy is usually a good thing.

One of the most commonly-cited papers in  the intermittent fasting literature is this one, which shows how short term fasting induces “profound” neuronal autophagy. Only that might not be true for both sexes; another study shows how while “male neurons” respond to starvation as we’d expect—by undergoing autophagy—”female neurons” respond by resisting autophagy.

Less autophagy isn’t necessarily a bad thing. Certain diseases take advantage of the autophagy process, turning it against us by clearing out and killing healthy cells, and women tend to be less vulnerable to these diseases. But if you’re a woman aiming for autophagy, fasting may not be as reliable an induction method.

My Conclusion…For Now

As it stands right now, I’d be inclined to agree that pre-menopausal (and perhaps peri-menopausal) women are more likely to have poor—or at least different—experiences with intermittent fasting (at least as a weight loss tool). That said, it appears to be a potentially gender-neutral therapeutic tool for chemotherapy, cancer, and age-related neurodegeneration patients.

So, Who Should and Who Shouldn’t Consider Fasting?

Have my recommendations changed?

If you haven’t satisfied the usual IF “pre-reqs,” like being fat-adapted, getting good and sufficient sleep, minimizing or mitigating stress, and exercising well (not too much and not too little), you should not fast.

These pre-reqs are absolutely crucial and non-negotiable, in my opinion—especially the fat-adaptation. In fact, I suspect that if an IF study was performed on sugar-burning women versus fat-adapted women, you’d see that the fat-burning beasts would perform better and suffer fewer (if any) maladaptations.

I would also caution against the already lean, already calorie-restricted woman jumping headfirst into IF. I mean, fasting is ultimately sending a message of scarcity to your body. That’s a powerful message that can get a powerful response from our bodies. If you’re already lean (which, depending on the degree of leanness, arguably sends a message of scarcity) and restricting calories (which definitely sends a message of scarcity), the response to fasting can be a little too powerful.

I’d also say that daily fasts, a la 16/8 or even 14/10, run the risk of becoming chronic stressors and should be approached with caution by women. Same goes for ultra-long fasts, like a 36 (or even 24) hour marathon.

Most of all, however, I’d simply suggest that women interested in fasting be cautious, be self-aware, and only do so if it comes naturally. It shouldn’t be a struggle (for anyone, really). It shouldn’t stop your cycle or make it harder for you to get pregnant. It should improve your life, not make it worse. If you find that fasting has those negative effects, stop doing it. It should happen WHEN (When Hunger Ensues Naturally), if it happens at all.

Some Warning Signs To Watch For

  • Weight Gain (especially in the midsection)
  • Insomnia
  • Muscle Loss or Reduced Performance In the Gym—It’s perfectly reasonable to suffer in the gym on fasting days, but watch out for persistent strength losses. If your fitness and strength levels are consistently trending downward, fasting may not work for you.
  • Infertility
  • Loss Of Your Period—Skip meals, not menstrual cycles.
  • Excessive Hunger—Feeling peckish is good for everyone and makes food taste better; constant satiation is a trap of modernity. But you shouldn’t be ravenous. Thoughts of food shouldn’t consume you.

The good news is that most of the ill effects of fasting are blatant and conspicuous. They don’t hide. They don’t lurk in the background. They’re really hard to ignore—so don’t!

Some Thoughts For Women Who Want to Fast

Instead of aiming for the longest fast you can tolerate, aim for the shortest fast that gives results. Don’t try to power through a 24 hour fast, braving headaches and foggy thinking and overpowering hunger. Do try eating dinner earlier so you get a good 12 hours of “fasting” simply by going to bed and eating breakfast at a normal time.

Don’t fast unless you have a good reason. Good reasons include:

  • Having significant amounts of fat to lose.
  • Your oncologist giving you the go-ahead to try using it to improve the effects of chemotherapy.
  • Your neurologist giving you the go-ahead to try using it to improve brain function in the face of cognitive decline or dementia.

Bad reasons include:

  • Keeping the pregnancy weight at bay.
  • Going from 15% body fat to 12%.
  • To boost your 5x weekly CrossFit sessions.

Men and women have inherent metabolic and hormonal differences, and it’s evident that these differences in part determine how we respond to a stressor like intermittent fasting. I’ve never prescribed intermittent fasting as a requisite piece of the Primal lifestyle, but rather as an elective addition, a personal choice—only as a potentially therapeutic strategy that each individual must test for him or herself. 

I generally fast when it makes sense – if I’m traveling and good food isn’t available, if I’m just not hungry, stuff like that. I periodically do 16/8 or 14/10 (i.e. eating in an 8 or 10 hour window) and find it works great for me because I am fully fat-adapted. But even I don’t hold rigidly to that. It’s not for everyone. And that hasn’t changed.

That’s it for me, today. What about you? If you’re a woman who has tried fasting, or know someone who fits the description, let us all know about your experiences. I’m intensely curious to hear from as many of you as I can. Thanks for reading.

By the way…because this is an updated version of a previous article (as I noted at the beginning), previous comments will still display. Keep in mind they may refer to the context of that previous article version. 

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570 thoughts on “Intermittent Fasting for Women: What We Know Now”

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    1. I got to the “So estrogen is a toxin in the body. The body’s always trying to
      detoxify and then metabolize so you’re rid of it” which was from the “expert” and I was done 🙁

  1. I fast regularly and have found no such problems. I generally do between 20-36 hour fasts a couple of times a week. I do fasted training also and find that by the end of the fast I feel rejuvenated not faint. I prefer how I feel in a fasted state than when I have eaten throughout the day. I feel it resets my body and its nice to take a break from eating.

    1. Er, that’s all well and good that all that works for you, whoever you are. But without the sex, age, and (if female) stage (pre-, peri-, or post-menopausal), it doesn’t tell me anything. What was your point?

        1. A woman disagreeing with someone does not warrant a “meow”, you are actively part of the problem.

        2. Yes, I hate it when guys do that. Perhaps a ‘woof, woof’ every time men were anything other than 100% agreeable with one another would be appropriate. (Although I’m sure Ron is charming . . . nothing personal) 😉

      1. Her point is that fasting is working for her brilliantly and thus may work for someone else. She is sharing her experience like everyone else…

        1. How do you know KM is she and not he? There is nothing in the post to indicate gender, thus my questions.

          I’m not trying to be catty (Rurgundy not withstanding), I’m trying to elicit information that I believe MIGHT illuminate whatever KM’s post was meant to illustrate. I’m trying to get him/her to SHARE MORE of his/her experience. Sheesh!

        2. Jodis – I am not certain but this post was directed at women so that is why I am assuming it is a women. I could be wrong…

      2. Actually, what KM wrote is the same for me. I am 52, post-menopausal. I am actually tired of most articles and bloggers like this Stefanie person stating that her findings are for ALL women when they are not. NOTHING is right for everyone. Everyone is different and what works for some don’t work for others – that includes IF, Paleo/Primal, low carb, etc. I think her POINT was that this woman and other writers should say this or that may or may not work for a people or a certain group. That IF article is like a blanket statement that IF won’t work for women with certain situations when that is often not true.

        It just comes down to what works for YOU and YOUR body – listen to YOURSELF and don’t believe all this stuff you read is set in stone. As Mark here on MDA says, keep an open mind.

        1. I actually agree with you but would like to point out that Martin over at Leangains has strongly instigated all of our physiology is alike, and that women can routinely IF too. As a woman who has tried his protocol on two separated occasions for 6+ weeks each time and has GAINED weight in the form of fat both times, despite tracking calories and other data, I am thrilled to see this post. I suspected my body was interpreting the fasting as a chronic stressor because it was making me want to binge eat, which is not something I get when I otherwise just eat primally. So while nothing works for everyone, I am glad to hear this generalization.

          1. I too have tried intermittent fasting twice, for approximately 6 weeks each time. Both times my overall weight loss stalled. I gained fat and lost muscle. This last time I lost 2 pounds of muscle and gained 2 pounds of fat. Not significant, but completely opposite of what I was attempting to accomplish. I’m active & not menopausal. I just don’t think IF is something that works for me.

          2. I respectfuly would like to disagree with this article. There’s a lot of opinions in there to discourage woman from ripping the benefits of fasting that are not backed up or followoed by “might”. I would not recomend it for thin women or teenage girla. However, if you have some weight to loose, there’s a lot of variations of fasting you can do. The first tip is dont go into this full turkey. Try pushing breasfast 1 hour later, then two… untill you can completely skip breakfast(One variation). You can do this a couple times per week, delending how you feel. Second, what you eat matters. After your fast eat veggiea, protein and fats in the form of meat, eggs, oatmeal, etc. If you eat pizza or other high caloric food you’re gling to feel very hungry and unconfortable when you fast. Look up “Ketogenic diet”. I apologize for the long post, but seriously this article madee me upset, so much misinformation. Hope it helps!

        2. I’ve had the same experience as the commenter who talks about gaining on the leangains protocol. After being stable at my weight for about 8 months, I started GAINING weight when I started IFing. Also, I experienced the opposite of people who say they got a handle on their binge eating. After a fast of anything over 16 hours, I eat like a starving lion. I can’t control myself. I don’t have this problem if I eat 2 or 3 meals everyday. The binging happens even if I’ve eaten a lot before the fast, so it’s not like I’m making up for lost calories. So rather than the fasting causing the weight, I think it’s the binging after.

          I have to admit, though, that I do have life stressors, so maybe that’s the problem. Then again, I doubt I’ll ever have NO stress.

        3. “Everyone is different and what works for some don’t work for others – that includes IF, Paleo/Primal, low carb, etc.”

          I totally agree with you ! Sometimes I’ve got the impression we are creating new religions with low-carb, veganism & lots of statements about health and what is correct for us (“because the last studies showed that…”)

          We got too much information & don’t listen to our body enough.

          I’m a 25 years old female & I feel great with IF. Sometimes with no breakfast, sometimes longer than 24 hours. Sometimes with fresh juices.
          With no rules, just the feeling.

        4. Agreed with this, there is no such animal as ALL women, we’re all individuals with various levels of similarity and difference. I think THE most useful take-away knowledge on nutrition is that there is just as you say- there is nothing that works for everyone. There’s no universal one-size-fits all.

          Also, IF works fine for me. I do daily fasts of 12hrs from waking up, then a 4hr meal window to drink wine and enjoy cooking and grazing as I choose, then fast the remaining 1-2hrs before I go to bed.

          This also allows me to just not bother with food period for most of the day. I have food intolerances and digestive issues and medication that has to be taken on an empty stomach, so it is SO much easier to just keep all that stuff penned up in one part of the day.

          I’m 33, at my ideal weight and having maintained it for 3+ years. I exercise daily (lots of long walks, and some sprints thrown in if/when I feel like it, lift heavy things if/when I feel like it). I’m 5’7, 120lbs, I eat about 2100 calories a day, and do about 110g protein, 50-60g carb and the rest from fats.

          I get lots of flak for doing it, since fasting is bad and not eating constantly in 6 small meals is bad and not eating grains is bad and not being vegan and eating murder-meat is bad and eating all that fat is bad and being a woman who doesn’t eat during the day is bad and blah blah blah blah. But it works fine for me. 🙂

          You’ve just kind of got to try stuff and see if it works for you. Don’t believe anyone’s blanket statements indeed.

        5. On the other hand (oh, I’m an overweight, post-meno., woman), Stephani’s entry was an amazing head-slapper for me! I’ve been adjusting my life, enjoying more than I can say being, if not a fat-burning beast yet, at least fat-adapted enough to enjoy NOT craving food at any particular time… I’ve been heading towards a more intentional IF. Instead of just waiting till I get hungry, I’ve been planning on doing longer / intentional fasts. (Right now, I often go from dinner till noon or 1 or 2 without really noticing (well, except my morning coffee) — so I’m doing some longish fasts, but not by plan.)

          The concept that maybe intentional (somewhat aggressive) IFing might NOT be the best thing for me never, ever entered my consciousness! As Mark wrote: the back-and-forth, the ‘hey, my experience / information is different’ interweb discussions are tremendously valuable, because they bring up ideas that may never occur otherwise!

          Definite vote for Stephani!

        6. I so agree with you! I am a 41-year chef and yoga teacher who also happens to be a pro fitness model, (I compete with several drug-free federations and you can find me in magazines like Oxygen and Inside Fitness). As a body-builder, experimenting with diet and training ad nauseum and whittling down to 8% bodyfat is what we have to do to win, and for me, (and quite a few of the other women on our team) cycling in really low-calorie, (700 kc) and no-carb days has resulted in great gains for us. Speaking only for myself, when I go 4 – 6 low days in a row, I start thriving on 6 hours of sleep, I get personal bests at the gym, I have tremendous energy and clarity, and feel generally more capable and strategic. In other words, I can multitask like nobody’s business and push through a high work load. I agree 100% that you have to do your homework and really develop some intuition for your body. The important thing is to figure out what works for you!

        7. I am a 43 year old woman who most of the time ate a ketogenic diet. Over the years I had slipped and gained weight from a lean size of 2 to a 4 with love handles! I thought I was doomed and it was hitting forty that ended my tone physique. However, that was not the case. It is all about food and making the right choice. I have been doing IF for two months and am back to size 2 (with no rigorous gym routine, just yoga and walking for cardio). I fit into jeans that are ten years old which shows me I have made progress and IF works. If it is not working for you, it’s because you are eating the WRONG foods, no other excuse. Or you are drinking alcohol and taking prescription drugs which could prevent you from taking off pounds.

        8. Just to add to the collection of testimonies for those interested:
          For my diet, I combine daily IF with high fat, grain free, leafy green predominant low carb and perhaps a few paleo principles (but NOTHING will keep me from my peanuts, peanut butter and purest love for fine aged and cottage cheeses)

          28 yo F serious endurance athlete (80 mi/wk on foot + 130 mi/wk biking – I have been training this way for about 4 years)

          Practicing daily IF (ranging as low as 12/12 up to 20/4) since March 2014. Along with a grain free low carb, high fat, low-moderate protein (up to ~150 gram of carbs/day which is up to 15% of total caloric intake on days I burn 5000+ calories).

          It took me about 3 months to fully adjust to my personalized eating plan

          But for the past 4 months, I feel like I’ve been thriving. The only reason I stop working out is I don’t have time to do more! I heal faster than when I was eating a traditional runners/endurance athlete carb heavy diet with grains, I sleep great now – like I used to as a kid before menstrual cycles tried to ruin my life.

          DIsclaimer: I have been taking an ultra low dose monophasic oral birth control pill for 10 years, so this could be a reason I haven’t noticed any menstrual irregularities with my diet

        9. I am 58, post-menopausal, female and couldn’t disagree with you more. What Stefanie told us in her article was a summary of the tiny bit of scientific information that is out there. Nothing more. You are reading more into it. She never said a blanket statement applying to all women. You are putting words in her mouth. The one conclusion she had, was that more study is needed. i fully agree. There is far too much male domination in the field ofscientic studies. Women’s special health effects are VERY often neglected. I was very happy to read about the different demographics of women who were actually studied, What I saw was that the decreases in fertility were the worst consequence of this diet, which only effects women of child bareing years. Both you and I are past our child bearing years. So of course, the worst side effect will not harm us. We might benefit greatly from the other good effects, including weight loss, lower LDL, lower cholesterol, increased brain functioning. That’s a real bonus for us. I’ve been on it 5 days now. I did experience the sleepless nights, pointed out in the study, that only women experience, not men. Now that I know why I am sleepless, I will stop blaming it on the coffee that I had in the early morning. Now that I know my brain function is improving, I might take advantage of it to get some studying done during those sleepless hours. It was VERY GOOD for me to see the results of these studies and how they affect my sex and age group. I am very happy to have this information.

          And of course, your main point is that every person is different. I wholeheartedly agree with the point that you are making as well. Your right in that every woman has to do what works best for her particlar body.

          When I was younger, most women skipped breakfast because we were always trying to live up to the unrealistic ideal of having a “Barbie” like figure. We all starved in the morning, and yet we all managed to have kids. Even the skinny girl who had trouble conceiving, eventually succeeded. I think her doctor told her to eat more. Then she was good to go.

          So if there is a young woman out there who wants to try this, I don’t think it will do any harm to go on a 12/12 hour fast. This is one of the fasts that Dr. Oz recommended for women on his show. Then if there are no bad health effects, (like no missed periods), then you may as well continue, like my friends and I did when we were younger.

        1. I hve tried IF and gained weight also.,.,im 48 yrs old and discouraged.,.,

    2. Her point is anecdotal but about as good as this article’s sources as well. Each “study” he cited had at most 8 women or female rats…. That is the worst and laughable sample size amount I have ever heard of. thats like a 30 percent margin for error so your data basically has no authority

      1. Exactly! Not cool when blanket statements made with flimsy support. That grehlin research linked that women’s levels rise faster than men’s only involved 8 men and 11 women, all obese. I would not call that rigorous and robust consensus, rather a single data point.

        Th

    1. Re the difference between men and women: no man with half a brain is going to touch that one with a ten foot pole.

      1. Isn’t ‘man with half a brain’ redundant?

        signed,
        Women everywhere

        1. Naw, naw… It’s not that you men only have half a brain, it’s that you’re only *using* half a brain. Robust corpus callosum for the win! 😉

        2. So that’s my problem – my corpus callosum isn’t working!

          Wonder if I’m only using the left or the right…..

          Hmmm…. perhaps if I get ready to jump off a roof… and my logical brain stops me… it’s the left I’m using, but if my artistic brain says Grok Swan Dive!… I must be using my right….

          Hey guys… watch this!!

        3. @Tracy: Is the comment ‘man with half a brain’ sexist and inappropriate too? Or good for the goose but not the gander?

        4. sexist and inappropriate 😉 – remember sexism doesn’t mean (inappropriately) discriminating because of female sex, but any sex.

      2. Or a 50 foot pole. There is differences between male and females but you can’t describe it I guess. You can say it but do you really get the point of it?

    2. The differences between women and the differences between men are greater than the differences between women and men, so lets get over this already and just talk about our individual experiences as people experimenting on ourselves.

  2. “Intermittent fasting…as a requisite piece of the Primal lifestyle, but rather as an adornment, a choice, a potentially therapeutic strategy that each individual must test for him or herself”.

    Well said!

    I think intermittent fasting works best when it is done randomly, as opposed to some set schedule. If i am not hungry for whatever reason, i will not eat. Simple as that. Do i fast intermittently weekly. No, not always. Sometimes i may fast a few times a week. Some weeks i may not fast at all. Some days i eat 1 meal, others 2, or even 5 or 6. Let your body dictate, i say.

    1. Right on. Super hot here in Chicago right now, not going to sprint, and pretty low appetite…this is how it’s supposed to work, right?

      1. Agree!
        IF or the compressed eating window of 8 hours, has really helped me listen to my bodys hunger signals, and make those signals clearer too.
        I love it! I eat when I am hungry, and I find that when I am fasting I am not as obsessed with food.

    2. Agreed – I have been using IF / EatStopEat patterns for the past couple of years. Not as regularly as I would like but I have sustained high levels of activity/calorie burning therefore need fuel for my body to use.

      That said – I do prefer randomly using fasts. I think this is more effective at ‘shocking’ my body into fat loss but equally more therapeutic. If I knew I had to fast every Thursday, I think it may become a bit of a chore and more likely to be skipped!

      1. “If I knew I had to fast every Thursday, I think it may become a bit of a chore and more likely to be skipped!”

        Yes, that is precisely how i feel, too.

    3. I would agree with this. This is exactly what I did when I fasted to lose weight. I didn’t force it. I would decide each day if I felt like doing it again, and throughout the day decide if it was right to keep on going or not. Always listening to the body. However I can’t do this anymore at or below 10% BF. The body now says no. I can do shorter fasts, not longer than say 17 hours.

  3. When I wrestled in high school I would sometimes go almost two days without any substantial food, but could still function even with high intensity workouts. My mom, on the other hand, could not go twelve hours without food. She starts feeling sick, neseus, and gets headaches. Almost like she is going into shock.

    1. 12 to 14 hours is about my limit, too, and that is overnight. Although I am in my 50s, I have never been able to go long without food, until I began eating Primally. Now, at least I can go 4 to 6 hours between meals without the low blood sugar blues. I also find when I start sneaking carbs back into my diet, I wake up ravenous in the middle of the night. Low carbs equals steady blood sugar and easier fasting.

      1. Yes! Also, of course, in advocating stepping carefully around fasting, I am in no way advocating grazing. I still believe people, broadly speaking, should eat 2-4 meals per day, just reasonably spaced.

        1. For the past 6 years, every day, i only eat between 7am to 2pm, the body takes time to adjust. I am a 47 yrs old female, not menopausal yet, and weighs just under 50kg. I guess this would not be IF as its daily? I find that not eating after 2pm allows me to wake up fresh and hungry. But i do not train paleo, but a yoga in the iyengar and ashtanga tradition for over10yrs.

        2. Just found you Stefani, with this post’s link. Great to read. Wonderful.
          I’m a 39 yr old woman, still breast-feeding my three year old (not exclusively- he’s a primal boy).
          My husband fasts pretty much daily and has become a machine on the primal diet although he ..?can’t eat breakfast- never has as an adult. So he IF’s on weekday mornings till lunchtime and some weekends, activity depending.
          I MUST have a full breakfast; greens cooked in garlic, fat and broth with nori flakes and egg yolks and a cheeky roasted drumstick for example. My second meal is meat/fish and veg around four in the afternoon and a snack like soup at night. Never felt better, looked stronger and healthier nor been happier.
          Husband would puke on this much food in the morning.
          I’d do the same from hunger if I skipped it.

          I took the IF post with a grain of salt (and most exercise posts too; with a toddler who needs it), leaving it to the body-build/sculpt types. Primal was never about weight management or becoming super-buff for my husband nor me.

          There is no way I’d try IF with little ones; I love MDA but one does incur odd whiffs of male locker room. Painless enough, but great to know you’re there in all your blinding female glory.
          Grrrrrrrr’rok on.
          : )

  4. Hugely appreciated this post, Mark. I’ve been noodling around with IF, but nothing to the point of having an impact on weight loss. But then, I’m still not fat-adapted, so there you go.

  5. I have dabbled in IF, eating only when I am hungry. I am a teacher, and getting up at ungodly hours sometimes renders me not in the mood for breakfast. It happens in fits and starts: sometimes I will skip breakfast three days in a row, other times I will go three weeks without missing my 2-egg omelet with cheddar, bacon, and spinach.

    Today, for instance, my tummy wanted nothing to do with breakfast — until I was on the road. I even looked at a Dunkin’ Dounuts with longing, wondering if I could just dismantle one of their newly advertised wraps and eat the bacon egg and cheese inside. With fortitude, I made it to school and ate my Greek yogurt with fruit and coconut “lunch” as my breakfast, saving my snacks (almonds, string cheese) to be consumed as needed until dinner. And I did not regret for a second driving by that fast “food.”

    When left to my own devices on weekends or days off, I usually eat my omelet (when I wake naturally without an alarm, I am always pleasantly hungry), and do not eat again until late afternoon; sometimes that means a late lunch, and sometimes that means just a snack (nuts, or string cheese) until dinner. I think I have skipped dinner all of once since going Primal, again, just because I was not hungry. I never hold off on eating for the sake of fasting, it just goes against my programming. I listen to my body, whether it tells me to skip breakfast or devour that Porterhouse, I do so.

  6. I’m a pre-menopausal woman and have been experimenting with longer fasts this week. I perceive myself has having more energy and focus and being happier and calmer. I have always had problem skin and the fasting appears to be clearing it up. It does seem harder to lift weights when I’m fasted, though.

    1. Hi new faster. Stefani here. That’s wonderful! I believe that some women do great on fasting, particularly if they are not stressed or already very fit or at a healthy weight. I also believe that an occasional fast for all women might do them well. I do, however, caution women against listening to their bodies a bit in this case.

      In fasting, a woman’s hormonal response may take a while to become dysregulated. However, something that happens right away is that a woman experiences increased energy. This may be due to upregulated adrenal function– ie, adrenaline, in the system– but it has also been shown both in animal and human studies to be a result of upregulated hippocampal function. Women become hyper-alert and increase their memory capacity when they are calorie-restricted or on rigorous fasting regimes. Researchers hypothesize that this is an evolutionary safeguard against starvation. Women also (and female rats) can start sleeping less well at night. All of these factors are because the woman is being provoked to be awake and energized enough to forage for food.

      So while this may feel good in the short term, I am wary that it may indicate longer-term hormonal dysregulation.

      Links supporting those arguments about starvation can be found in my original article on fasting

      1. Ha! love that! Hormones! 46 years old…love the hormones…hate the hormones…nothing is consistent in my life and I often have to pick and choose which direction to follow in the primal lifestyle based on what my body is telling me. Thank you Stefani for talking about this. I am so tired of people expecting my body to react like a mans when it most clearly is NOT.
        brick

      2. I’ve noticed this for me. I’ll occasionally (one morning every few months or so) use fasting to increase my productivity for a work project when I have a lot to do and not much motivation, but it does leave me rather sleepless later that night. Like you mention, I’d read somewhere previously that fasting increases focus and energy, which is hypothesized to help us better seek out and find food. I think we tend to see more focus and productivity as a good thing, when that may not always be the case.

      3. Thank you for this!! I am a 44 year old premenopausal woman who is, let’s just say,”not lean”. I tried IF and almost immediately stopped sleeping and experienced interruptions in my menstrual cycle.

        I continued to IF, and things improved in the sleep and cycle department. However, since reading your article I have discontinued it, as I was not losing weight on it and also I realized that my body had trying to tell me something!

      4. My HGH increases during a fast, and I sleep like a baby. Burned off 2 1/2 lbs last night while I slept!

    2. It took me almost a year to be adopted to exercising in a fasted state. After adaptation it became amazing – like never be able to became tired.
      I am 51, eating a LC diet since Nov.2007. It manages all my pre-menopausal symptoms and other health issues, like migraines, I’ve never got even a seasonal flue since I started my diet. IF is a part of LC eating for me. If you are adopted to ketosis, then practicing IF is the next logical step.

    3. I am 24, F. ( 5’6, 125lbs ) I used to do IF last summer, and dropped a lot of weight and looked great for my bday. Also maintained around that wight for a long time without IF.

      I started IF again this week, 16-8, because i have been having a harder time losing a few lbs and also just feeling sluggish and feeling always hungry or constantly snacking, since I just got my Masters, looking for jobs and spend a lot of time at home, also recently quit smoking(3 months ago). So these past 3 days of me doing IF, also walking a lot, I have dropped 3 lbs, and I feel so much better, a lot more alert, my skin cleared up, (which was something I experienced last summer, my skin had never looked so good), my stomach feels so much nicer when I wake up, I feel calmer and happier! I also think that trick is to lower the amount of carbs you are consuming, make sure you eat lots of greens, and get enough potassium, also maybe if you have hard time sleeping, eat your last meal closer to bedtime and make sure its filling. I have actually been sleeping more after doing that.

      Definitely agree, that this is not something I will be doing all the time, especially if I start feeling emaciated, but it’s a great tool to try and see if it can work for you.

  7. I am a 47yo female. I generally don’t eat past dinner (7pm or so), I work out early (6am or so) after a cup of coffee, and I don’t eat breakfast until 9am or so – some days not until 11 if I’m not hungry. It’s just what I do – I don’t (or didn’t) consider it IF, and it’s not something I tried to do consciously.

    Replying to vmckenna’s Mom’s response to fasting – I used to feel like that, before I started eating this way. Sick/headachy/mean after a few hours not eating. It made a huge difference once I was no longer carb-fueled. Now I can be hungry, and that’s all it is – just hunger. The world no longer has to stop for me till I feed myself 🙂

  8. Evolutionarily speaking, why (and how) would men and women evolve to thrive under different circumstances/in different food environments? That’s the question on my mind since reading Stefani’s posts.

    Thank you for writing about this Mark, I was hoping you would weigh in!

    1. Well, just to take a stab at this… I’d have to say, in the traditional hunter/gather approach, since women didn’t wander away for too long to find food, they probably had more steady access to nutrients. It probably has a LOT to do with reproductive health too – Someone who’s pregnant or breastfeeding itsn’t going to be out hunting with the guys… Men probably adapted over time (and women) to the environment they were by. Women probably had more access to the nuts, berries, plants, roots, marrow, broths, etc., and men probably had more less access and were forced to fast/gorge when the opportunity presented itself.

      This probably varied by community and practices and climate.

      It makes sense to me, but I have nothing to back it up. Research time…

      1. Makes sense to me, although I think women did make long trips to known locations of food. Keep in mind that Grokina (and Grok) had limited means of carrying food home. You can hang a dead eland on a pole and two guys can carry it. What if you find some nice berries on the way to a melon patch. It makes sense that you eat them some. But if you are tracking an animal, you keep moving, maybe all day, or for several days.

        1. If we’re talking purely hunter/gatherer people, and not idealized fictions, food on hunting trips isn’t as scarce as you might think. They brought along foods like pemmican, jerky, and anything else that could be stored and easily munched. When they caught their quarry, the first thing they would do is cut it open and eat the organs, which wouldn’t keep long otherwise. Some would eat the liver raw, others might start a fire to cook the heart, kidneys, and sweetbreads. Organ meat, being the most nutritious, was the boon of hunters. You can see in wild animals that hunt today that the organs are still the most prized and first eaten.

          Conversely, a woman’s ability to starve might do more for her reproductive fitness than you might think. Everyone is worried about pregnancy and nursing, but a mother’s job isn’t ended when the child is weaned. Living with food insecurity as a child, I saw my own mother often fast so that I could eat. And honestly…it isn’t uncommon for families living close to the edge, for women to starve so their children can eat. Like people have this weird idealized fiction of happy perfectly adapted cavemen, but there’s a reason we breed at a rate fast enough to cause overpopulation in modern society–we used to die a lot more. The food wasn’t to blame, but sometimes the lack of it was. I’m not happy with this revisionist idea that men had no access to food while women did. It isn’t scientific to cherrypick some facts about modern life, then extrapolate a fantasy of how cavemen made us this way without fully understanding causation or having any way of testing or researching these theories, that actually goes against paleo by assuming any difference in the sexes is set in stone and not a possible result of differences in modern lifestyles.

    2. It is really hard to say how it would have been back in the Paleo era, but I would imagine that women would not only have foraged for berries, nuts, roots and small animals closer to camp… they may have also done it packing an infant on their back and dragging a toddler along behind.

      Also, it is a female’s nature (and I have noted this behaviour in modern times) for a woman to give her rations to her children and make due with no/less/inferior food herself.

      1. My sister bow hunts for deer. She would never have stayed back at “camp”or “just” foraged for berries and herbs. She always gets her first shot and drops a buck where he stands. She can carry it out of the woods after she field dresses it. She is amazing. She has an IQ of 155. She uses herbs for healing. She knows where to forage for them even in the city. She would have packed her child on her back as she hunted and protected them with her life. At age 50 she can out lift and out work most men half her age.She looks 20 years younger. Only 5’2″ and 125 pounds. Paleo. I also find it hard to say what would have been, but I believe there were woman with her same independant spirit.

    3. I don’t think you should ask how they thrived, but how they survived at the worst times. What this difference points to is that in times of starvation, Females generally have a reduced ability to conceive. It makes perfect sense, since a pregnancy will leave the mother very weak if she cannot get enough food. Could miscarry or not have enough energy for delivery, or not be able to breast feed after, all these things killing the women and children of women whose bodies allowed pregnancy during starvation.

    4. Well, this is something I do know something about! It has to do with the very different costs of reproduction for men and women. A fullterm pregnancy costs around 78,500 calories, and milk production costs 90.13 calories/100g. Lactating for four years (the average for hunter-gatherer societies and chimpanzees), plus the pregnancy, costs around 1 million calories. Add to this the costs of the supplemental foods gathered and prepared by the mother, and the costs of carrying the infant. Forager women do most of the provisioning of their children. All this adds up to a very powerful selective pressure toward women being highly efficient at extracting calories and storing them as body fat, possibly explaining why women carry just under twice as much fat as men of the same ethnicity, height, and weight. Men who die of starvation have ~2% dissectible fat, women around 10%. Certainly women who are very well provisioned can get their fat below 10%, but I wouldn’t recommend it, especially not longterm. Lean Hadza and Himba women have 20-24% body fat.

      As to activity, women in foraging societies engage in sustained, calorically-expensive activities. They dig up tubers, pound nuts, scrape meat off bones and connective tissue on hides. A forager woman may walk several miles, several days a week, carrying a four-year old on one hip, a baby in the belly, and a kaross with 30lb or more of underground storage organs, plus digging sticks and a skin of water. This is very different from the kind of energy expended by men, whose hunting or honeying expeditions may occur only a couple of times a month, and that require walking followed by explosive bursts of energy.

      In hunter-gatherer societies, women provide anything from 34-90% of the calories eaten by the group – that’s right, the men may well be dependent on the women for steady access to calories and nutrients. Grokina didn’t skulk helplesslyin a cave with her even more helpless infants until Grok came home with a hunk of eland! Grok often came home empty-handed, and sated his hunger with the tubers roasted by his mate or his mother, perhaps with a relish of berries and lizards pounded together, or a dish of stew of tender leaves and rabbit, maybe with some wild grass seeds to thicken it up.

      Early male anthropologists were very into the hunting aspect, especially of big game. It wasn’t unknown for the shellfish, netted fish, mice, lizards, birds, tortoises, and scavenged kills supplied by the women to be lumped into “gathered foods” that were then assumed to be all plant foods.

      1. I was not aware that breastfeeding burned that many calories. Now I know why my body ended up eating my muscles. I was making over a gallon of milk/ day before my son was introduced to solids and we continued nursing until he was 13 months. On top of what used to be a higher-than-average metabolism and what seemed like an incredibly restrictive diet, my body just couldn’t take it. I ended up about 20 lbs below my healthy weight. If your numbers are right, there were months where I was burning more than 3,400 calories/day just making milk. I cannot imagine having to do that without a grocery store nearby.

  9. I gotta say, this kinda freaks me out. I’ve been doing IF for a few years now. I do one meal a day (dinner) which, for me is very satisfying because I enjoy eating large quantities and this allows me to do that without fretting that I am taking in too many calories. Am I hungry during the day? Yeah. Sometimes I am. But I hold out for my nightly feast. I am extremely active and lean but muscular. I have not had my period for about 3 years, but this was the case long before I started IF, when I was diligently eating every few hours. I do have some issues with night eating, but I wouldn’t say I have severe sleep problems–I sleep pretty darn well fairly often. Could I be doing serious damage?

    1. Are you eating enough calories? I’m not against feasting at one meal per day but if you aren’t getting in enough calories in that one meal, you may be doing your reproductive system a disservice.

      1. Hi Michele. I would ask about calories and your weight status, too. It sounds like you are possibly running in an energy deficit– one of the most prevalent causes of amenorrhea. In this case, it doesn’t matter when you eat–hence why you still were amenorrheic before–but how much you eat (I would argue however that when is still important.)

        There are a variety of things that can signal to a woman’s body that she is starving. Lots of exercise, low body fat, low caloric intake, possibly fasting, and possibly low carbohydrate intake are all culprits. As well as high stress. Here’s the work I’ve done laying out the subject: http://www.paleoforwomen.com/category/hypothalamic-amenorrhea/ and specifically for you I think in this post:
        http://www.paleoforwomen.com/the-hpa-axis-metabolic-distress-and-hypothalamic-amenorrhea/
        And I recommend checking out the fertile thoughts forum, http://www.fertilethoughts.org, in order to get a good taste of what women with hypothalamic amenorrhea experience.

        Menstruating is not necessary for health, but it IS necessary for fertility, as well as for having a healthy sex drive. Additionally, I would bet that you possibly have low estrogen levels, which is a concern for bone strength and the formation of osteopenia. A simple blood test should tell you whether or not that’s an issue.

        Low estrogen, and low levels of pituitary hormones LH and FSH are the key markers for hypothalamic amenorrhea, if you do decide to get tested.

        Best,
        Stefani

        1. I am 4’10” and weigh about 107-110 lbs. I am small but muscular. When I eat my one meal I EAT. I honestly have no idea even ballpark how many calories I am taking in but I am always quite full when I finish eating. I am also on birth control but had been on it for several years before my period stopped. I also just got off crutches for a stress fracture in my hip which makes me think you could be right regarding my bone strength. What should I be doing? I’m also terrified of change and this has become a very convenient way for me to operate so I’m pretty nervous about moving forward here…

        2. I am a successful, published fitness model, with a year round BF of 11% and competition BF of 8-9% and I have never taken hormones or lost my period. I know a ton of other women like me, so making a blanket statement like this about what is healthy for women just seems absurd in the face of reality…

          1. Really Michelle who cares about your being a fitness model? Gosh you go on & on about this – Seems you like to brag a lot.

    2. i started if’ing in january of this year and haven’t had a period since. that’s 6th months. i’m definitely not pregnant. i’ve lost about 10lbs since and i’m active. i don’t think about it too much because i feel the best i’ve ever felt in my life. best mind, spirit and body i’ve ever had. every once in awhile i do think though…yikes. is this a problem?

      1. It can be. Not menstruating in itself is okay for health, but it DOES mean that your hormones are out of their desired balance. It also might mean that your adrenals are working overtime, which is why you are both losing weight and feeling really good.

        The best well known health risk of amenorrhea comes from having low estrogen levels, which leads to osteoporosis. Also, with amenorrhea, the uterine lining continues to thicken, such that endometriosis and endometrial cancer can become real concerns over the long term. Hormonal imbalance can also lead to insomnia, anxiety, and mental health problems down the road– but that depends on how much they are dysregulated and for how long. It varies by individual, so I am not trying to encourage you to act one way or another. Just laying out for you what some of the common amenorrheic complications are.

        1. Hi ladies,
          I had just recently had my blood tests done for the same reason, no period since August last year. I had been playing with IF only around 2 weeks before that so I don’t know whether it had any impact on the results or not. My estrogen level is very low and my GP recommends I go back on the contraception pill which I don’t really want to do to be honest.
          Stefani, is there any other way how to raise my estrogen? Should I stop with IF? Thank you.

    3. It’s not OK not to menstruate. It’s really not. It’s a sign that something is wrong! Usually it seems to be the chronic caloric deficit rather than level of body fat that is the problem. Leigh Peele also says she sees it more in people who do lots of intense full-body workouts vs split routines.

      I’ve had stress fractures and they measured my bone density which was low in my spine. There is nothing that brings you back to reality faster than realising that you’re putting yourself at risk of fractures. What you do now is impacting your future. I know I really, really don’t want my future to consist of hip/vertebral body fractures and a hump.

      I strongly recommend you get it sorted!

      1. I just wanted to add my two cents to the menstration conversation. I had lost my period on and off and than completely for close to a year. I was concerned about fertility and a loss in sex drive, and my obgyn just suggested BC or Colmatin (not sure on that name, but something to induce ovulation) as a “solution”. I wasn’t satisfied with that answer, so I went to a Integrative Doctor (wonderful, highly recommend, integrative medicine over western. More holistic, looking at all parts of the body and mind as interconnected) who did blood work and a saliva test and confirmed I was dreadfully low in testosterone, really high in estrogen (no periods, no where for the estrogen to go). Cortisol was shot and I was suffering from severe adrenal fatigue. I’ve since been working to increase testosterone and progesterone, balance out the hormones, increase my cortisol, rebuild my adrenal glands. Feel 100% times better.
        In my case my body was pulling from everywhere, eventually my testosterone… Trying to find help in dealing with day to day stresses.
        Bottom line, irregular periods are a sign (in my opinion) that your body is not functioning at optimum health. Address the causes, not just the issue (with BC)… P.S cycle is now regular every 30 days!

        1. Do you continue to IF? I have all the same signs of hormone deregulation and I’m curious how you regulated. Thanks!

      2. Doesn’t it really depend on her age (which she doesn’t mention)? She could be menopausal (pre- or not). This is a part of nature. Our hormones change because they are supposed to. Of course if she is younger, she might want to investigate other reasons, but menopause can happen as early as in one’s 20s. It doesn’t necessarily mean there’s anything else wrong. Also, there is a correlation between eating meat and dairy and lack of bone density. Look it up. Hope you feel better soon.

    4. My HGH increases during a fast, and I sleep like a baby. Burned off 2 1/2 lbs last night while I slept! But, here is the thing, I have fat to burn. Fasted rats and people with nothing to burn aren’t going to do as well. The body will then burn protein, yikes, that is true starvation.

  10. My wife and I have been doing a version of IF from the BulletProof Exec guy – basically coffee w/ Kerrygold butter & MCT oil for breakfast. I’m feeling great on it, and it helped push me past a weight loss plateau. But she’s getting an upset stomach from it and not going anywhere on her weight loss. I’m guessing she’s not fully fat-adapted yet. I just ordered her some super-enzymes per the Bulletproof guy’s recommendation. We’ve been primal for over a year now, but my wife takes more of an 80/20 approach. Is that going to prevent her from being fully fat-adapted? Any other ideas?

    1. I do not think it’s necessarily a matter of being fat adapted or not. Perhaps… I would suggest if you are both invested in this protocol that she go 100 percent rather than 80/20 and see what happens. (You never know, right?) Then you might know whether or not the fasting works for her. Perhaps she is one of the women who responds poorly to fasting, and instead of losing weight actually ends up with a body that responds by storing weight.

      1. I am a 46 year old woman. Lost my cycle Dec 2014 and have been on a weight lose plateau for just as long. I decided to IF BulletProof style all last week and dropped 7.2 pounds without any struggle at all. I also got my cycle back. Go figure. I’ve got a new tool in my bag and I’m loving it because I felt completely in tune with myself, was more alert, acutely more aware of smell. My focus was off the chain, did not have hunger pains and saved $$$ on a weeks grocery bill.

    2. Ryan, I respond the same way as your wife to IF – when I am without food for more than 4 hrs I feel very ill & get an upset tummy. I am 33, female & only been primal for 3 months and follow it 100percent! I have leaky gut which I think is a huge factor in why I don’t do well with IF. With a compromised gut I am unable to produce enzymes to digest food and make nutrients available for absorbtion so I need to eat 4 meals a day. Along with eating primal I am also following an anti-candida diet (and removed FODMAPs) to help heal my gut. I also take digestive enzymes as your wife does which has helped a little but it’s not a cure. I supplement with L-glutamine to help repair my mucosal barrier & probiotics to restore gut flora. I doubt I will be able to benefit from IF until I have healed properly & can start absorbing a decent amount of nutrients – it may take months!

      1. What your doing sounds similar to the GAPS diet. Don’t forget to eat bone broth.

    3. If I am not 100% primal, it takes about 3 days total fasting for me to get into ketosis and I suffer headaches and I feel tired and hungry.

      If I am 100% primal, it takes a day and a night, very little hunger, and I wake up thinner and in ketosis, so I feel good.

      I am a female, 45.

  11. Eating very low carb and fasting made me an insomniac for the first time in my life and caused gobs of hair to fall out. I’m in my late 20’s and have PCOS. I think the prior symptoms have to do with increased cortisol.

    1. I don’t have PCOS but I had the exact same issues. I started Primal with a low carb and occasional fasting regiment and it was not pretty. I’m in my early 20’s, and things got irregular, my hair, starting falling out and I started waking up at 3 AM every night. I upped my carbs and stopped fasting, and immediately things got better.

      1. *my hair started falling out.

        I hate when I don’t read things over before I hit post. 🙂

      2. Waking up at 3 a.m. every morning is an adrenal fatigue (and possibly thyroid) symptom! (Read up at Stop the Thyroid Madness: http://stopthethyroidmadness.com/long-and-pathetic/) Look in the mirror and see if the outer-third of your eyebrows are gone/thinned )(thyroid). Hair dry and straw-like (and/or falling out)? (thyroid/adrenal)

        (Many, maybe most (modern) women have both thyroid and adrenal fatigue / problems.) I used to wake up feeling like someone had taken a bat to my kidneys (adrenal), the soles of my feet hurt (adrenal), my neck hurt and I was stiff and achy (adrenal/thyroid). WAY too sensitive to light and noise (as if I were hung-over!) (adrenal) (Who know?)

        Having now treated (over several years) first my adrenals and then thyroid (thyroid treatment won’t “take” if your adrenals are still under-functioning) — I cannot begin to express how much healthier I feel! No more morning hang-overs, no aches and pain, actually started some weight loss again!

        (My thyroid doc said — and it’s very very very very hard to find a GOOD doc — like for so many of these “paleo” (non-AMA/pharma/CW)-type things: ‘you can have an exactly correct diet, and be exercising like crazy, but if your thyroid is screwed up, you’re not likely to lose an oz!’

        So, like so many of these health things– you have to SELF-educate (not necessarily self-medicate — but absolutely educate!), cause your medical practitioner probably won’t know anything *correct* about it!

        (Oh, the 3 a.m. thing? Your body runs out of energy, and so your poor tired adrenals whack you with some adrenaline, which wakes you up. The ‘carbs before sleep’ let you sleep… That’s also why your morning coffee can make the stiffness or tiredness go away — coffee whacks your poor tired adrenals to perform.) (Beatin’ a dead horse … er … almost-dead gland is not optimal.)

        1. EXACTLY. I was just too lazy to explain it all. I’m very much in the beginning of fully healing.

    2. I would agree. I spend a lot of time researching and talking with women who are not overweight and have PCOS. I believe this is the case because we (I am one of them) have struggled with metabolic dysregulation and poor insulin metabolism in the past… and now that we have either lost weight or undertaken stressful diets and lifestyles, we have the additional “stop sign” on our reproductive system from this new angle. So far as I can tell from talking this over with women, the best solution is to eat a paleo, low-insulin, anti-inflammatory diet while simultaneously keeping psychological and metabolic stressors to a minimum.

      1. Hey Stefani,
        I first read about this on your blog and was surprised when I saw it here today! Can you elaborate on a “paleo, low insulin, anti-inflammatory diet”. I’ve had digestion issues for about 18 mos, causing me to be on a low carb diet, and now have low everything… Magnesium, testosterone, T3, B12, and amenorrhea. Being tested for candida too. Any guidance would be appreciated! And your blog is so informative! Thx!

    3. Yup, me too. I lost weight on low carb primal with IF but my hair was falling out (A LOT) within 4 months. I’m in my late 20’s with PCOS as well. My cycle regulated during that time though and I felt great. I’m attributing the hair loss to the low thyroid effects of low carb. I now eat about 100g carbs daily, fast no more than 14 hrs (overnight) and don’t snack betweeen meals. This is lowering insulin and keeping my cycle normal and the weight continues to drop!… as long as I don’t snack or eat after dinner. And no more hair falling out :).

  12. I’m a pre-menopausal female who tried fasting during your series. I thought I was doing alternate-day-fasting, but as your series progressed, I realized I was doing it incorrectly. Basically, I skipped breakfast and lunch every other day or ever 2 days, for several 24-hour fasts each week. I did it for about a month and lost 5 pounds. I am one of your rare readers who did not experience weight loss when I went Primal (alone). I still needed to restrict calories, apparently.

    What I liked: it obviously worked for weight loss, and it gave me more flexibility for social situations and work lunches, so I didn’t have to deprive myself quite as much when I did eat. It was very doable, and I found I was less hungry throughout the day when I didn’t eat at all than when I ate restricted calories.

    What I didn’t like: I relied a lot on caffeine, which felt wrong to me but necessary to get through the day. I also had a few situations where I overate when I got the chance to eat, which also made me feel really bad.

    All in all, a successful experiment but I probably will not fast this way again. I still think there is a place for a weekly 24-hour fast but for now I’m restricting daily calories (plus eating Primal) to lose the last 5 pounds.

    I should also mention that I can’t speak to menstruation because, long medical story, I don’t get a period.

    1. That is a problem I find with IF’ing. If I skip breakfast I sometimes find myself over eating at lunch and I then find myself craving something sweet..as if I need a boost of energy…I don’t like that. But if I eat 3 meals a day for too many days in a row, my weight either maintains, or climbs 1-2 pounds…so I have to switch it up. Very frustrating, because I can not lose on Primal, but it does help me maintain.

  13. Hi Mark et al,

    Stefani here. First, yes!, I recently (this weekend) ran some stats on some new web analytic software and found that the one I have been using for years underestimates by 50-100 percent. (I had been using compete.com and just switched to Google software). My enormous apologies in that regard. Sincerely. I take intellectual honesty more seriously than perhaps anything else, so it means the world to me to apologize to you and convey to you that that was a mistake. And trust me, those low-ball numbers did nothing for my message, either. It would have made my message more powerful to cover the true vast expanse of your readership.

    Moreover, I would like for you and everyone to know that my ‘targeting’ of you for the research was a matter of your popularity and role as a prime figure head. I wanted to demonstrate to whoever read the blogpost just how popular and somewhat gender-skewed fasting literature has become. The surest way to do so was to point to your work and to your readership. Which I love, which I love so dearly, and for which I am so grateful.

    Third, I cannot say enough how much of a happy (but not surprised) relief to find us on the same side. My work at my blog in no way has rabble rousing as its primary end. While unapologetically ‘calling you out,’ as I hope I made clear in the post and in my writing here, I only did that in order to push strongly for an awareness that I believe deserves attention–from all of us throughout the community, big and small. In all cases, my goal is health. Real, true, holistic health, for everybody. I write specifically for women because I believe there are needs that women have– over and above the simple fact of having ovaries– that are not necessarily flushed out as well as they could be by the general paleo world as it has unfolded so far. This includes reproductive fitness and how to achieve hormonal balance as well as the nuanced difficulties of female fat loss, and also, importantly, the unique relationship that women have with food and with their bodies. Sometimes I speak plainly on the science, but sometimes the science requires a louder voice than usual to be heard or to make a difference in the world. This is when I happily allow my fists to come up, if always in a holistically loving way, a la the post at http://www.freetheanimal.com.

    All that said, I agree, too, that fasting has enormous benefits for cancer and other diseases of civilization, and I do encourage people to undertake fasting as they see fit. It is only, as we both agree, that knowledge and awareness are nothing but power.

    The first of many replies I will be making on this post, I am sure. 🙂

    1. “I recently (this weekend) ran some stats on some new web analytic software and found that the one I have been using for years underestimates by 50-100 percent.”

      I’m confused–underestimates *what* by 50-100%?

  14. And just to clarify – a lot of people say they feel more energetic while fasting – I do too. But that isn’t necessarily a good thing just as drinking too much caffeine isn’t either. You’re making your adrenals work harder to produce more cortisol. And the body steals the building bLocks of progesterone and estrogen to do it. Not good! Stefani’s blog is a must read.

    1. Lex, the cortisol thing is not so much a problem when you are fat-adapted. It’s when you are a sugar burner and can’t access and/or burn fat as easily that the adrenals are called upon to start the catabolic process.

      1. I beg to differ. I did a very low carb diet – about 30 to 40 carbs or less a day while not eating any sugar for months – for a while not a tad. And that’s when the hair issue was at its worst. Also, when I started sprinting and weight lifting while eating this way I had insomnia. I could not figure out why I woke up after 3 or 4 hours until I understood I must have low cortisol. The body relies on that when blood sugar levels go low. If there isn’t enough cortisol your body uses adrenaline and then you’re up for good that night despite how crappy and sleepy you feel.

        1. This doesn’t sound like anything I have ever read or learned from personal experience. For starters, your cortisol is SUPPOSED to be low at night.

          I went for decades where my cortisol was high at night and low in morning and all the way up until the mid-afternoon. So, I couldn’t sleep at night. And, yes, I went to an actual medical professional and had actual tests done which actually proved that was what was happening..

          Also, I don’t know what you were doing to be “low carb” but I have noticed a lot of people do it by limiting their vegetables all told and increasing their protein. Which, too much protein screws up your hormone levels and not having enough potassium from your non-starchy vegetable sources will screw them up, too – making it where you crave carbs and cannot sleep.

          30 -40 grams of carbs may also be way too much for you. Or, they may have been the wrong carbs. There is a LOT to be taken into consideration. Just because you think you were doing it right doesn’t mean you were doing it right for you.

          Really, I thought what was going to be the main subject of this post was not really even touched on, which is that yes, men and women are different, but, that doesn’t mean that women cant’ fast. It means that if a woman eats the portions recommended for a man, she is less likely to lose weight. And, women are more likely to need vegetables and less likely to need giant amounts of protein.

          Just like a smaller person needs less food than a bigger person, and, a non-weight lifter and a weight lifter are probably going to need different amounts of food, all told, including different ratios of fats/carbs and proteins.

          Even an individual person can fluctuate on their needs. Maybe one day you need lots of vegetables and no other protein and another day you need 6 oz. of protein and three avocados. These things happen.

          I did notice when you said you were doing a low carb diet you didn’t mention your fat intake. How did that go?

      2. What are some signs that can help me determine if I am ‘fat adapted?’

      3. Thank you, Lex, Mark. There is another issue for women at stake in this compared to men, in my opinion. Women often experience a fasting “high” of mental clarity, improved memory, and alertness (both rats and humans). While this feels great and I myself really enjoy using it, it is in fact a real evolutionary adaptation built in to prevent starvation. The female body (but not the male body) increases hippocampal activity in response to fasting conditions. For this reason other effects include insomnia and potential anxiety, depending on the degree of the starved state detected. The whole point being that women “masculinize” (in the researchers words) and become super foragers in order to help them find food. Not necessarily a good thing for us in the modern world.
        Links to this research can be found in my original post on the matter if anyone’s interested in exploring it further. http://www.paleoforwomen.com/shattering-the-myth-of-fasting-for-women-a-review-of-female-specific-responses-to-fasting-in-the-literature/
        I’d also be thrilled to talk about it more as I find it to be both fascinating and important.
        Best
        Stefani

        1. Thanks for responding, Stefani. I think this is such an important thing to get the word out about. In these comments and in the forums you see all these women saying, but I feel amazing! And I don’t want to burst their bubble, but I’m tempted to ask, but how long will you feel good? How long will it take for your thyroid to get so jacked up you start losing tons of hair. Maybe longer than me but it doesn’t mean we weren’t on the same trajectory when went super low carb and fasted.

        2. I am wondering when you are speaking of these reactions to IF for women how long are the fasting states?

        3. Hi Stefani,

          Is this because IF lowers Estrogen and increases Prog in women?

      4. Kudos to you Mark. The best teachers I know, are open minded, continue to learn and know… the more they know, the more there is to know. Great article.

    2. For the sake of candor, I have fasted regularly since adolescence. I am 53 post menopausal and so healthy, it frightens me at times! The only times I ever missed a period was due to pregnancy. I have two children, 22 and almost 20; they were unplanned. They were full term and the labor for first was 1.5 hours and for the second 45 minutes.
      Upon entering menopause, even eating primal and exercising I gained a lot of weight, as I did with my pregnancies. 5’6” usually 127 pounds, then a high of 168 pounds with all vitals text book.
      I have just completed a 21 day water fast and have never felt better. I now weigh about 138 on my way back to 127 or so.
      I must say that I disagree with Stefani although I appreciate the efforts. As modern humans, male and female, I am convinced that we are adapted for fasting. We simply did not have food all the time. The only way across species the we have determined of prolonging life and maintaining health is through calorie restriction. Fasting appears to turn on the Sirtunin genes which prolongs life in males and females.
      This notion of excessive individuality is an indulgence. Of course we are different. Yet I submit that we are more alike that different. As groups of hunter-gatherers we probably ate pretty much the same according to the particular environment.
      I would not suggest any degree of fasting while pregnant or nursing. I don’t think it far fetched to imagine that among our ancestors, those women were given food in times of scarcity.
      Otherwise there were times we all fasted.
      Perhaps the hyper-attention was yet another gift bestowed by Nature on females to allow them to feed their children.

      1. Karen, sure, women in a particular group of hunter-gatherers would all eat much the same food. But they wouldn’t all respond the same way! Children (male and female) whose genetic makeup was less efficient for that particular diet would be more likely to die around weaning. Girls would take longer to reach puberty, have fewer children, and their children would be less healthy. Some 50% of !Kung San women don’t ever have grandchildren, and that’s the important thing.

        This effect of individual variability can be seen in non-human primates. Not all chimpanzee females thrive on the diet they all – with minor variations -eat. Not all have the same level of reproductive success. Male chimpanzees are not all equally big and strong; some are runty. An indulgence? No. Mother Nature’s way of ensuring that, even under changing conditions, there will be some individuals suited to the new conditions (they may have been the runts in a previous situation) who will survive and breed successfully.

      2. Lovely comment!

        I am wondering, when you say you fasted regularly since adolescence, what that means? I mean.. how often? Why? When? That sort of thing. It’s not often I hear /read from someone who has so much practical experience in the matter. Please tell us more. Or, do you have some sort of blog related to such experiences?

  15. Since becoming fat adapted I am less hungry in general. I eat WHEN and that usually ends up being a heckuva scramble and coffee or tea mid-day, a couple of snacks (handful of nuts, berries, or meat, or even a paleo-ized baked good I whipped up for the kids- gotta taste test ya know!) and dinner within the next 8-9 hours.

    This pretty much evens out to me being 16/8 – 14/10 most days. I’m continuing to grow slimmer, sleeping better, constantly getting compliments on my skin, and my menstrual cycle is more regular and efficient than ever before in my life.

    We recently went through a move, and during that time I was succumbing to convenience of carbs. I ate more and more often, slept less, and felt crappy. I was relieved to gety kitchen in order and resume my regular eating routine.

  16. I was able to do a 24 hour fast once a week when I was in my weight-losing phase. Now that I’m fairly lean (and eating somewhat higher carbs), it is too hard to go that long without eating. I attempted fast-5 style fasting and it totally made me crazy, obsessive, unhappy and hungry. I’ve decided that eating healthy primal food is best and to focus my efforts on improving my body composition through exercise. I’m sprinting and doing calisthenics which is new for me and giving me good results. I’m 47 and getting more toned and muscular and I like it.

  17. I find that I ‘IF’ naturally, and have had no real ill effects. I actually feel that it has helped my postpartum body recoup faster than it did with my son. I only eat WHEN, and sometimes that doesn’t occur in a 24 hour period. Much like KM wrote, I usually feel better on fasting days then on days where I am eating regularly. I also don’t overeat after a fast, which can’t be said for my pre-primal state. I also used to suffer from hypoglycemia and fasting was absolutely not an option, as my body would shut down under emergency mode, and I would be physically unable to move for almost an hour while someone shoved crackers and juice in my mouth to get me back on my feet. I’m a far cry from that now, and actually function optimally whether I am IF-ing or not. It’s pretty amazing how far my body has come in such a short amount of time! 🙂

    1. “WHEN”–here it is again! What does it stand for, please?

  18. Mark, I found this article very interesting and informative. I am a 49 year old woman who is pre-menopausal (I’m guessing). I’ve been struggling with my weight (I gained 30 pounds after 3 rounds of prednisone for serious allergies) after I had my 4th child at the age of 42. Lots of things going on there…my thyroid numbers are “normal” by in a range that could, according to new studies, be indicative of hypothyroid. I haven’t been able to lose the 30 pounds (plus the other 10 or so that I still wanted to lose after my daughter was born. I was that close to my pre-pregnancy weight when the allergies hit).
    I do well on primal–feel better, more energy, etc. but I’m not really losing a lot of weight. Kind of stabilized–whether I do primal or not now.
    My exercise regime consists of regular walks, some hand weights, trying to be active with my daughter (I’m a single mom) and so on. In the past, that was enough to keep me fit and trim. Not now….
    Not sure what all is working against me: sedentary job, pre-menopause, thyroid, previous prednisone weight gain (and whatever really causes that–effect on thyroid, etc.).

    1. Off the IF topic, but I wanted to reply…
      Theresa, I have found that adding a little bit of high-energy movement every the day helps a lot. I also have a sedentary job, tho I follow Mark’s workout three days a week (body-weight exercise M,F, sprints W). I have been adding just a little more movement to each day, lately. Swimming a half hour a couple times a week. Hula-hooping for 10 minutes a few times a week. Jumping rope every once in a while for 5 minutes.
      It is still an effort for me to remember to do it, but the fun factor convinces me. Maybe you like music and could get
      up and really dance out to a good song?
      It’ll get easier, too, as your youngest gets a little older – you’ll have more freedom to spend time on yourself again. Mine’s 9 and there is a huge difference in me-time after those short two years.

  19. As a woman on the other side of 50, I consider myself doing the IF when I put off breakfast until 10:00. I find it too over-welming to think about fasting for extended periods of time (which for me would be anything over 12 hours). I also have a teenage daughter that I am trying to model good eating habits for. She seems to have a healthy body image so I guess I don’t see IF as an enhancement to our lives.

    1. That being said, I have tried IF…fasting until around 11:00 AM and have had no problems with it at all. Not sure I’ve seen a benefit, but no problems either.

      1. Oops—that was supposed to be an additional comment for my previous post.

  20. I have fasted with no problems. My type of fasting is when I’m not hungery and a mealtime comes around a’ll just skip that meal.

  21. Another major caveat I’d give to IF is that people who struggle with cravings and binges (REAL binges, not just choosing to have a handful of cookies once in a while) should not fast.

    But eating a big protein breakfast over time kills the cravings and naturally reduces hunger, so that now I’m naturally skipping lunch every day, with no hunger, and none of the increase in cravings I always used to see when I tried IF w/o the high protein&fat bkfst.

  22. One of my issues is getting cold when fasting. Only happens once I hit the 12 hour mark. Other times it doesn’t bother me at all. I think eating sugar as part of my last meal (ie fruit, honey, maple syrup and sugar) is what is doing it.

    I really try the WHEN approach. It feels so much better to me then any other type of IF.

  23. I am 28 (fem) and I started a 24 hour intermittent fast (eat at dinner time) around 3 weeks ago. I have had no problems with it. Occasionally I feel hungry, if I drink some water it tends to go away. It’s made me feel good overall. If I do get actually hungry, I will eat during the day. And on my nature hikes on the weekend, I break my fast with bacon and eggs before going, to make sure I have fuel for the exercise. I think IF is great (though my family hates me doing it) and it has helped me lose weight. 🙂 I don’t plan to do it forever, and I’m not terribly strict about it. WHEN always applies!

    1. Weird that your family hates on you for doing it, mine does too. I can’t figure out WHY, lol. Maybe it’s just too much blasphemy against CW, dunno. I’m close to you in age and also a gal.

  24. I’m 45, primal for about 3 years but still a bit over my desired weight- but I’m insanely chronically stressed, so I’m OK with maintenance until I finish my dissertation. At some point I’d seen some research to suggest that men do better on ~17 hr IF, while ~14 hr is better for women. I’ve definitely found 14 hours to be my sweet spot — much longer and even if I don’t get hungry, I get jittery and scattered. I don’t plan my IF, rather let my body be my guide — I bring a meal to work, and when I feel ready to eat it, I do. sometimes that’s 9am, sometimes 1pm. It seems to work 🙂

  25. I have been intermittent fasting since October 2010. It wasn’t intentional, but just kind of happened. My pattern is typically a 14-18 hour fast and then two large meals with the occasional snack. I have been a low-carber for more than a decade so I am definitely fat-adapted. In the same time period as I have been fasting I also have been in the final leg of recovering from adrenal fatigue. My doctor is aware of my low-carb and fasting status and is fine with it. In fact my most recent salivary cortisol was the best it has been in nearly four years. Fasting was never something I forced my body to do, it happened naturally and has been a great way to effortlessly maintain my weight and enjoy great food! I don’t have issues with sleep, sex hormones or micronutrient deficiencies, eat high-quality food and supplement wisely. Oh and I also get very comprehensive lab work done every six months or so.

    1. Can you say more about the “very comprehensive lab work”? Like, what you have tested and whether you go directly to an independent lab or how you get your doctor to agree/order testing, etc.

      Is that how you know about your micronutrient levels?

  26. Had to chuckle when I read this. I’m peri-menopausal and didn’t realize I was basically fasting (14/10) until I ran into a horrible bout of insomnia — waking up between 1am & 3am and not sleeping much after that. Turned out that I was waking up because my body was freakin HUNGRY, even though my stomach wasn’t rumbling. Had to add a bit of starch/fiber to my diet (primarily sweet potatoes) and I no longer worry about wanting a snack before bedtime — sleep is back. No fasting for me — too stressful on my system.

  27. I’m so glad to see this article! I personally have experienced good weight loss results with IF every once in a while after a weekend of indulgence or too much straying off the blueprint, but the successes were generally very modest ones. My husband, however, has great results with IF.

    After Mark’s series, I gave fasted weight training a try for the sake of experiment and gave it up after a few goes. I just don’t do well on heavy lifting days when I’m fasted. No strength, no muscle recovery in between sets – I much prefer to be fed. I have so much better results!

    1. I never did well working out fasted either. My workouts were lame when fasted. I much prefer fed workouts and I’ve had great results as well. The shape I’ve gotten into speaks for itself.

    2. I recently said I could not work out fasted. Well, I finally tried it again two weeks ago and I’m working out fasted now and it’s AWESOME. I’m not sure what changed. I’m thinking my mindset. I’m too lean to do 24 hour fasts anymore. I can do them but I tend to want to eat everything in the fridge for a couple hours after each meal for several days afterwards and that is just torture so I stopped fasting.

      Since I can’t do the longer fasts, I decided to try working out fasted first thing in the morning and then not eating for 2 hours after the workout. The only thing I had to do differently was lower the intensity of the cardio I do for the 2nd half of my workout. Oh my gosh this works awesome for me. I’m leaning out for an event and it’s WORKING. I eat dinner anywhere from 5-8 pm the night before. Wake up and have black tea and head to the gym. This allows me to have possibly 15-17 hour fasts and the workouts at the end help me get the HGH benefit. I’m quite happy with this solution.

  28. I would have never believed that fasting can come naturally (without forcing yourself to NOT eat). Only two weeks into my experimenting with eating primal, I wasn’t hungry. I skipped eating for one whole day.

    Getting over carbs was also interesting. I ate oatmeal with flaxseed for breakfast for over 3 years, so switching to eggs and bacon was wierd. I felt like I was cheating on a diet or something.

  29. 22 year old, very lean female. Into weight training, parkour, and general athletics. I tend to, like Mark, use IF as a tool. If I’m traveling, at a non-Paleo dinner party, or don’t have time/supplies to pack my lunch or funds to eat out. Probably once or twice a month. I haven’t had any trouble fasting, it really comes naturally and I even find it a bit rejuvenating. I tend to scale down my workouts but honestly I have plenty of energy.
    Side note: I did not lose weight when I went primal (didn’t have any TO lose) put actually was able to build muscle (sleek, not bulky) very quickly and easily.

    1. I’m not sure that skipping a meal twice a month is considered fasting? The article posted by Stefani from “Paleoforwomen.com” was about the problems females tend to face when regularly fasting and for much longer periods of time. I think she would agree that skipping bad meals is a pretty good call.

  30. Thanks for this insightful post Mark! I’m also grateful for the idea to not eat when you’re not hungry, it makes sense! Several times a week I (47, 5’8 and 150, from the Netherlands) do not eat after 7 pm and then start eating 11 am the next day. I believe that is considered a fast? Only since I started eating Primal I can do this very easily and love the “clear” feeling it gives. Would like to lose 10 pounds, hope this short fasting will help, besides doing more exercise. XOMO

  31. The one and only time I made a conscious effort to IF, my body really wasn’t happy.
    I track my body temps and noticed that they really plummet if I’m fasting which can’t be a good thing. Also I’m tired and cranky.
    Having said that, if I just don’t eat because I’m not hungry I’m generally fine.
    Conclusion: IF is not for me, I’ll continue to just listen to my body and pay attention to its cues.

    1. One way to test and track thyroid ‘operation’ is through temperature tracking. My temps (still) are always well below 98.6… Before I treated my adrenals and thyroid, I was usually around 95-96; and no enzymes work well at that body-temp! Higher now, but still not “normal.” And yes, I’m still taking T3-only thyroid pills (down to one a day though — from six a day at my highest!

  32. I’m a woman and I just do it naturally… sometimes I just won’t want to eat for twelve hours or so and not be particularly hungry in general, and other times I’ll just need to eat a lot. I find the latter is dependent on hormones.
    I have a circadian rhythm disorder as a confounding factor though, so it’s possible that my eating cycle is not properly in line with my sleep at any given time.

  33. Having found intermittent fasting a massive struggle before committing to Primal eating, I confess I raised a sceptical eyebrow at the notion I might someday find it so natural I’d do it without thinking! But nowadays it really is pretty much effortless. I stick in the occasional timed fast if I feel I need one, but something I love about the “not IF, but WHEN” approach is the even greater freedom from counting – first calories, now hours since last eating! Not sure what the claim is for women not fasting, but considering we have higher body fat to draw on, I’d say Nature neatly planned for the likelihood we, too, may occasionally go without!

    1. I’m with you Rachel.
      I am 50, only vaguely aware of my cycle as I don’t have a uterus anymore, but I eat WHEN, and have since I did the Leptin reset, and then went primal, have been for about a year. I usually start the day with a coffee and cream (yum), then eat when hungry, about lunch time. Then cook for the family. I feel liberated from calories routine and guilt, and the kilos are slowly coming away. My PCOS symptoms are gone along with a whole host of other things. My sleep is a bit ordinary at the moment, but I have been a bit addicted to my iPad at the moment, so am going to switch to knitting by the fire in the evenings to improve that. I do have thyroid issues (been bumping along the bottom of “normal” for years), but I think this and liver function is gradually improving.
      If I know my day is going to be hectic, I will have eggs for breakfast, to fuel the day. But if the day turns out pear shaped, then like Mark, I simply wait until I can eat. No sugar crashes, no hunger. Some days though I need to eat, so I do. Great discussion everyone, though I think we need to be curious and aware of what we are doing, I wouldn’t over think it too much,
      Cheers

  34. I tried fasting with the 10/14 window. It did not go well for me. I was constantly hungry even though being low carb high fat. I gained a bit a weight or stalled completely. Now, the context for me is that I have PCOS ( hormone imbalance) and I did not meet the pre-req in the sleep department. ( waking with baby) My take away is that fasting regularly is not for me right now. With three young children I have plenty of stressors. Now, that said, when circumstances call for it, I can go much longer between meals if I have to. Being fat-adapted has been great for me that way. Thanks for the post, Mark.

  35. I am a guy who stubbornly resisted fasting for 2 1/2 years because I was getting pretty good results. After starting mostly eating in a mostly 11 am to 6:30 pm window, I am getting fabulous results. Fat melting off and twice as much energy. I think IF is essential for guys (after becoming fat adapted, which is also essential.) That’s how we hunter Groks evolved.

    But it is wonderful to see some thought about how women differ. Too little of that in medical research.

  36. I’m a 40 year old female. I’ve been primal for many years. I have to agree that complete fasting has never worked well for me. However I do find that making sure that I fast for 12-14 hours each night from 7 pm on and working out right away in the morning at 60 % of my max heart rate for 30 min before eating anything and waiting at least an hour after my workout to eat a primal breakfast has really helped me on my way to trimming the last of the stubborn fat.

    I have dropped double digit body fat percentage by doing this and nothing else had even caused a budge in months.

    1. Great stuff!

      Yes, that is a great way to practice IF for many people. Others i know prefer to eat lots at night and eat little or nothing in the morning hours. Both work.

      1. I am glad to hear this! I can naturally IF as long as I allow myself to eat heavy at night. I have trouble shaking the notion that you have to eat your biggest meal in the morning. Maybe my natural window of eating is 1pm to 9pm.

  37. Reading these posts just makes it even more clear there are differences even amoung individuals. We are each so different in how our bodies handles IF.

  38. I think that too many women interpret “IF” for “intentional starving”. I tend to go a day without food – or IF after a big food day as a result of a large family gathering or Sunday football or whatever- basically a cheat day. Honestly, I am not hungry the next day and IF just makes sense for me. It also gets me right back on track with my diet and weight. I strongly believe that some women read about IF and they’ll under eat overall and then not eat for a full day or more than a full day and they’ll do this repeatedly.

    I’ve never taken IF to mean that I should intentionally starve myself. I have used it as a tool to recover from a “bad” day or sometimes to help me get out of my own way so to speak. I think we have all said -“but I’m not eating that much” and well, we are. Sometimes IF helps you re-adjust your stomach capacity and get it to a more reasonable volume.

    Eat when your hungry. Don’t overeat. If you overeat, you’ll need to compensate. Enter IF. I think it’s fairly simple.

  39. I’m 62, post-meno, diabetic (no meds), pcos, met syndrome. I have good blood sugars, labs and have been IF between 14/10 and 16/8 for more than a year. I start the day with coconut oil and have a good protein lunch around noon. Between five and seven I’ll have a bowl of berries and nuts with more coconut oil.

    I feel fine on that schedule, but I haven’t lost any weight for ten years. I could lose 50-60 pounds yet but everything stopped at menopause. :p If this is hard on adrenals, I’ll start eating a light breakfast again!

    Sleep is compromised by arthritis pain, which I know doesn’t help.

  40. Till last year, I was fasting ~16 hours everyday for 45 days on a sugar adapted body. I never experienced any side effects. I am very lean with body fat around 17 – 20%(keeps varying every year). I usually let go of exercise completely during fasting because my sugar level drops too low.
    I have to fast every year because of religious reasons(I’m a Muslim….and we fast for an entire month called Ramadan). This year I’m more paleo than before, so I’ll be on the lookout for what changes occur in my body while fasting.

  41. I follow most of Mark’s advice but in 2 years haven’t really done IF. just did not come to me naturally and I wasn’t comfortable when I did force my self to try it. So I guess it really depends on how you feel and the results you’re getting and if you feel you really need to push your self enough to try it. If you’re happy with what you’re doing and the results you’re getting you may not want to push yourself that far.

  42. I’m a nursing mother and with my first child I was concerned about the fasting requirements of my faith (Catholicism) during the season of Lent (every Friday no meat and only two small meals that when combine do not equal a full meal). I had no idea what a fast would do to my already taxed body. Then I found a fellow mom blogger who posted her results which were not good: http://awomansplaceis.blogspot.com/2011/03/nursing-and-fasting-just-dont-do-it.html?m=1

    The Catholic church does abrogate children, pregnant moms, nursing moms, and the elderly from participating in a fast.

    I think it is important to know what will happen or has the potential to happen to a woman who chooses to fast. There needs to be studies done on the male/female differences. We are not the same.

  43. I’ve never had much faith in rat studies because rats are rats, not human beings.

    After quite a bit of experimenting, I find that what works best for me, a female, is a light breakfast, a light lunch, and having my main meal unfashionably early in the evening, say 5:30 p.m. or so. I don’t snack or eat again until around 8:00 a.m. the next morning. As far as I’m concerned, this is enough of a fast.

    1. As an update, after happening across this earlier post, I now (almost 6 yrs later) do IF pretty much daily from an early dinner until close to noon the following day. During this period I don’t eat anything and drink only plain green tea and water. I’ve been doing this for several years now. I don’t get hungry if I skip breakfast. It seems to be what my body prefers.

  44. Well I’m a 43 year old female (5’6″ 135 lbs) and I’ve dabbled in IF over the past three years. It does work best for me when I am totally random. I am fat-adapted and always do my workouts first thing in the morning in a fasted state. I’ve had really good strength gains this way and some weight loss. Most of all though I just try to pay attention and eat when I am actually hungry. I will say that it is is much easier in the winter time, when I generally am less active and sleeping more. In the summer time I barely fast (maybe 14 hours a couple times a week) since I am a lot more active. I’ve tried the 24 hour every other day type fasting also but that did not work very well for me. The best scenario for me is just a shortened eating window – maybe from 9-10am until 5-6pm or so. I also still eat the same amount of food/calories that I normally would – it definitely does not work when I try to restrict calories also.

    1. Ditto the question. It would be great to have a page of definitions/brief explanations of the jargon used on this site.

  45. Finally! I can’t tell you how many times I would read a discussion or get involved in a conversation and some well meaning man will tell me how my body is suppose to work. I am a 46 year old woman, 8 years of perimenopause. What works for me one month is no guarantee it will work the next month. I have done the IF. I can’t do it regularly..although it would be very easy for me to do so. In fact I would prefer to skip breakfast altogether, but when I do my body puts weight on. I have to shake it up. Go some days with IF and other days force myself to eat breakfast, even though I am not hungry. I can eat mushrooms for days in a row then sudden start gaining weight and have to drop them from my eating plan. I do like how I feel after IF…I feel lighter, cleaner, but in truth it doesn’t really affect my weight. I might drop a pound or two, but it doesn’t stay that way. Frankly, I am convinced it all has to do with hormones and how erratic they are in this time of my life, but it sure makes it hard to feel healthy when there is so much inconsistency with weight. Would love to see some posts about women in their 40′ and 50’s perimenopause and primal lifestyle. there is just not enough information and experiences to help navigate this crazy time of our lives. Thanks Mark and I hope to see more!
    brick

    1. brick – there is a thread on the forum for women over 50, but anyone can chime in. You may find some other women going through the change with advice or at least sympathy for you!

    2. Hey Brick! I’ve had posts stewing in my head on paleo, womanhood, and menopause for quite some time. They’re coming on my end, promise. 🙂

      Stefani

  46. 32 yo, f, I start the week with a 24 hr fast followed by 16/8 (usually 9:00/9:30 – 1/1:30pm), primal for 3 years, at the gym at 6:30 5 days a week for intense training then off to desk job for 11/12 hours, cycle has been away since I started this program of IF…. At this point my body usually gets hungry around the 14/15th hour, usually I wait until the 16th to eat, perhaps I should scale back a little but it’s tough when I’m trying to lose the saddlebags

  47. I tried AD fasting for four weeks. It wasn’t unbearable, and I didn’t have any bothersome side effects. However, I didn’t get much in the way of results, either.

    At first it seemed really promising. I lost six pounds in the first week and a half. But I was tired and spacey on the fast days, and when my weight stayed the same for the rest of the month, I returned to normal eating. Four of the six pounds returned almost immediately, which makes me think some of my weight loss was water.

    All in all, not a big success.

      1. I’d also like to add this: no one but my husband even noticed I wasn’t eating every other 24 hours. I’ve never made a dietary change that met with less resistance. I found this creepy.

  48. I’ve been doing IF for years. While coming from a background of PCOS and infrequent, irregular periods, it hasn’t been an issue with me for many years. Adopting IF made no difference, and quite possibly improved the situation. My periods are perfectly regular.

    I also never have weight issues while eating my optimal primal diet and doing IF and have absolutely no issues with energy. The only possible side effect is that I don’t sleep much – 6 hours a night. But this might just be optimal for me since I always feel great.

    Occasionally I have noticed feeling a little panicky after not having eaten for too long. This is likely due to my body trying to regulate blood sugar with cortisol. The occasions in which this has happened I have eaten and recovered within minutes. I think I may have gone too long without food for my particular body and needs.

    1. “I think I may have gone too long without food for my particular body and needs”.

      I think this to be correct.

      Another way to mute this panicky feeling besides eating is with intense exercise. Intense exercise can blunt hunger and many of its side effects.

      1. Looks to me like she feels as though her body is asking for nourishment, not more stress. If she worked out she’d just have to eat more eventually.

  49. I tried IF for a while, going with a 10 hour eating window. My experience was what Stefani describes. I felt alert and energized. BUT, then I would crash after 5-6 days and feel my adrenal fatigue symptoms return. When I went back to eating breakfast I started to wake up in the morning feeling like I had actually slept, something I haven’t felt for years while battling fatigue. My breakfast varies, quite often it is just bacon, blueberries and a handful of walnuts. It doesn’t need to be big, but it does need to be part of my day.

    Thanks Mark!

    1. I think you were fasting too regularly. Do it when you are not hungry.

      If i eat a meal composed of a lot of fat plus good carbs, i am satisfied for a long time and can easily skip meals.

  50. 41 yo pre-menipausal f. Primal since April 2011. I drop a lot of weight early in my Primal journey. I leveled off after about 6 months.

    I found that over the summer last year, IF was doable even though I was changing lots of things in my life. I skipped many meals just because I wasn’t hungry.

    As summer waned, I found I couldn’t maintain the same IF routine. I had to eat more over the winter. Weight however, maintained.

    Now that summer has returned, my appetite is going away again. So far, no more significant weight loss.

  51. I am a 37 year old breast feeding mom of two. IF has been incredibly variable in terms of comfort and efficacy. Most of the time, I would have coffee with cream (or butter) in the morning and then a late breakfast or early lunch. My husband does very well fasting. We’ve often remarked at how differently we respond to IF. I think the ultimate point is that we need to learn to listen to our bodies, fast when appropriate, and not fast when we are under stress.

    It is also true that women who conceive in a fasted or protein/fat restricted state will be more likely to have girls than boys, as girls are more likely to survive infancy than male babies. Of course, that is on average, not absolute!

  52. I am a 35 year old woman and have been fasting once a month as a part of my religious practice for over 20 years. Hence, fasting was not a foreign concept.

    I am new (3 months) to the primal lifestyle and have added IF into my routine once or twice a week. I have four children, and am no longer worried about fertility, so that is not a part of the equation for me.

    I have had a very positive experience with IF. I feel great during and after. I do 24 hour fasts and find that, it not only resets my body, but it brings me mental clarity, a general calm and a greater awareness of habitual/stress eating that I tend to do.
    Perhaps this comes from my years of fasting with a religious intention.

    I have also noticed a huge difference in fasting, now that I am a fat burner. I used to get headaches and obsess about food early in my fasting. I have not had any headaches during or after and I only get hungry at about hour 22.

  53. I tried fasting 24 hours once a week last summer for about 2 months, convinced it would be healthy for me. I was 38 yrs old and at a healthy weight at 130 pounds and had been fat adapted for at least 5 years. I felt fine while fasting, plenty energetic, clear headed, up until about the 20th to 22nd hours, when I got low energy and unmotivated. The fasting in combination with high stress, being very low carb (30 grams a day) and a lot of exercise resulted in intense carb/sugar cravings and subsequent adrenal fatigue, both of which led to weight gain. I will never fast again! I suspected there must be gender differences and am happy to have this issue addressed.

    1. I am guessing you fasted too long, that is all. It is not necessary to not eat for that long. Simply skip a meal or two when you are not hungry and that will do the trick.

    2. I have similar experiences at about hour 21, so I break my fast then. I am 33 and at a similar weight. Since I am moderately tall and fairly active, I just accept that IF can be part of my life but extended fasting seems beyond what is good for me. I find it too bad as I expect I would experience some much needed improvements in gut inflammation if I extended my fast. And I am fat adapted.

  54. I’m pre menopausal, fat adapted and I was happy to see this article. I know guys how have had great results with IF but it has honestly done nothing for me. It hasn’t improved weight loss but made me very hungry which I normally am not.
    A long term fast however is a different story. I have done 10+ days water fast with great results.

  55. I am a 44 year old female and started IF about 5 weeks ago. I do 3 – 24 hour fasts per week.It seems to agree with me quite well; I`m more alert, energetic and have also dropped a bit of weight. The main difference though has been nothing short of miraculous and here`s why. I have suffered with peri oral dermatitis chronically for the last two years and had tried everything to get rid of it. I had more or less given up any hope of getting rid of it and was reluctantly learning to live with it. Well, about a week and a half into the fasting routine I noticed a significant improvement in my skin and by two and a half weeks in I had a 75% improvement. Now, I would say that my skin is 95% better and I couldn`t be happier. I`m assuming that since my body is getting a rest from constant digestion, it can perform other healing duties. I hope that this may help someone else suffering with some sort of skin condition.

  56. I didn’t lose much weight at first but after ‘letting IF happen’ I’ve lost 50 lbs since November ’11. That is, I let myself eat when I’m hungry and it just happens. Two days ago, for example, I ate two eggs in the morning and didn’t eat again until last night. I feel extremely clear headed and have steady energy when I do this. Besides the weight loss, it seems like my moods are way more stable, and periods are like clockwork with barely any pms. Could just be improved diet in generally, I have no way to know for sure.
    If I try to force a fast, however, I turn into evil incarnate:) Following hunger cues is simple enough, and it works, so I’ll go with it.

    26 year old female, 3 babies, started paleo/primal eating around July ’11.

  57. To everybody starting chemo or knowing someone who’s gonna start chemo: FAST!

    Really, I’ve fasted through 3 rounds, to find I cope better each time. Blood work healthy for a non-chemo woman. Oncologist says I “do” really well. This round, nr 4, I ate normal (pretty Primal), because I thought they wanted to operate first (and bad health news concerning my mom made me forget), and OMG, I am totally floored. My husband says the difference is amazing.

    I love to eat, fasting does not make me happy or feel good, but this is so remarkable I share it where I can. Hopefully round 5 and 6 will be better, then I really proved something!

  58. I am a 34 year old female, and IF everyday. Usually 16-18 hours, sometimes less if I’m hungry, sometimes more if I’m not. I cycle macros, and have carb refeeds. I weight train 3 days a week fasted, and I can’t imagine not doing that. I love it. I am the leanest I have every been. I sleep well, I am not hungry in the mornings, and I have regular periods AS LONG as my calories are sufficient. If my caloric intake drops too low, it will affect my period, regardless of IF. I think fasting is just like every other piece of diet advice, if it works for you do it, if it doesn’t don’t do it.

    1. Great reply Kate! “I think fasting is just like every other piece of diet advice, if it works for you do it, if it doesn’t don’t do it.”

  59. I’ve been doing IF for a year and a half now and it really suits me (female, 29 years old). Usually I get up in the morning, no need to stress with breakfast which always made me nauseous in the past, go to work, go home again at noon (I know I’m lucky! In every sense but moneywise), do some laundry, gardening, grocery shopping or whatever needs to be done, then do my workout, then I put the kettle on and I eat my first meal at around 2-2.30 pm. Later I eat dinner with my partner when he gets home from work, and then I eat my last meal maybe around 9-10 pm while watching a movie or serie episode. I’ve been feeling great, so much better with the nausea, crankiness and lightheadedness that used to be a part of my everyday life before when I hadn’t eaten for like three hours.

    But still this gets me a little worried since we very recently started trying for a baby. Do I need to be worried and shall I start forcing food down my throat again in the mornings (sure hope not)? I’ve been on the pill for many years, then I got off them a couple of years ago and my period didn’t return for like 1½ years. But now it’s here, it’s more regular than it ever was back in my teens and it’s no longer a total blood bath, which were two of the reasons why I started with the pill in the first place. But what happens if I do get pregnant? Can IF potentially be dangerous for me of the little one, even if I’m feeling great? Cos then I’ll stop immediately of course.

    1. After having 3, I’m going to go ahead and guess that your feelings about food will be so strong that you won’t really care what anyone has to say about IF. You’ll either be so nauseous that you won’t even want to think about food, or you’ll be so ravenous that you’ll eat anything that remotely looks or smells like food!

      Seriously, though (although I was being kinda serious!), I think the same rule of listening to your body applies. I don’t think trying any new schedules is a good idea. This is also true after the baby is born. Although my weird sensitivities to food went away after our babies were born, my hunger did not and even increased! I don’t think there is any need to count calories while you are breast feeding. For me, a year of breast feeding plus eating primal took all the weight off.

      1. Thanks a lot for the reply. Of course I’ll have to see what happens and how I feel, as you say I might HAVE TO eat the whole world at some point or maybe I won’t be able to eat at all. I think I’ll stay this way for now anyway, as long as I seem to be thriving.

        But speeking of nausea it seems a bit weird to me if a mild IF like 16/8 or 14/10 would be harmful, since early on in a pregnancy many women aren’t able to eat much at all, and what little goes down may come right back up. That’s what I call serious CR.

        1. Right, but IFing does not perform the same function as vomiting food that was put in the stomach. Women can vomit for a variety of different reasons.

          I have never vomited in all 8 pregnancies (5 term), but with my only girl, I had wicked nausea and spent hours every day, for weeks, salivating into a bucket, feeling like I would (and didn’t), until I increased my thyroid supplement. It didn’t happen again, even once. My stomach returned to being settled and I didn’t have even one bout of nausea again.

          So IFing in my case is certainly not the equivalent of losing food I ate, due to hypo-thyroid. I have known other women who were having morning sickness, vomiting, and thyroid was the issue.

          I don’t think that vomiting is an optimal pregnancy experience indicating health. It may be normal, but I don’t think it’s healthy.

          Imagine from an evolutionary perspective that pregnant women would toss valuable and potentially scarce nutrients into the bushes; hunter-gatherers would most certainly have at least incidentally selected for women who gestate without squandering the tribe’s food while being weak and nauseous every day.

          I don’t imagine that what is normal and expected in our civilized societies is adaptive to a successful species, for a lot of reasons. 🙂

          Incidentally not eating at usual meal times and eating when hungry makes the most sense under healthy circumstances, when pregnant. Babies in utero don’t fast. 🙂

  60. this was a great article. i’m quite a tiny lady & have wondered about fasting. i really don’t see the need for fasting in my life right now, but this was a good read, nevertheless.

  61. Hi Mark,

    I haven’t fully adopted the Paleo path yet, so perhaps I am not the best source for feedback. However, I have had great success with IF in my weight loss endeavors, and I wanted to share that, at least, with you and your readers. I am a 30-year-old female who, a little over a year ago, lost 30 pounds to reach my healthy “goal weight.” I did this through mindful eating and old lessons I had learn as a former Weight Watchers devotee — namely, portion control. I found, however, that WW didn’t care so much about the KINDS of foods I was eating — as long as I was keeping calories down. That’s where I started to veer from that path and pay attention to not just how much I am eating, but what I am eating. Anyway. I had lost the weight and was feeling great — but my biggest challenge was (and is) keeping that weight off. In this instance I am not so different from a great many people reading your blog, I bet. I found IF and have worked it into my lifestyle — and it has allowed me to keep the weight off for over a year. I fast twice per week. My husband and I cook 5 nights a week and eat out twice a week. I have found that I am able to be very successful — both physically and mentally — by allowing myself to eat a little bit more on the “out” nights and then fasting the following day. Those “out” dinners aren’t made up of total binge food, but I definitely am not concerned about portion control or food weight at these meals (vs. all other meals throughout the week), and I eat accordingly. The next day, as long as my body allows me to (because I listen to my body first and foremost), I fast. It has worked out beautifully, as I alluded to, for both my mental and physical health. (Mental = allowing myself 2 treat meals/week; physical = not just the weight loss but improved blood work, etc.)

    So that’s my story. IF works for me. Thanks for another great post on the subject!

    Ashley

  62. IF’s totally wreaked havoc with my fertility. I wasn’t doing anything crazy, just skipping a meal here…a couple of meals there….I’ve been BP fasting for almost 2 months(ish) now and my period is already back on track and I feel and look awesome. I’m still getting the health benefits from fasting, but without the caloric restriction, which is what I would peg as the big downside for women who want to IF. As a woman who is BP fasting, I can now have my cake and ,ahem, eat it too. Check out the bulletproofexec.com if you want to learn more about bulletproof fasting.
    Thanks Mark for this post, it was very humble of you and just shows how sincere you are in your quest to help people.

  63. I’m 45, 5’9″, 192 lbs., and have been perimenopausal for 5-6 years now. I’m also pre-diabetic. I eat low carb/high fat, and currently use an 18/6 IF schedule.

    I started IF because I still have a significant amount of fat to lose, but my deeply entrenched habit of compulsive, mindless snacking stalled out my weight loss. I wasn’t gaining, but I spent several months not losing an ounce.

    My first, tentative IF schedule was 12/12, but within a week it shifted to 16/18 after I decided to see just how long it would take me to get truly hungry. It’s now 18/6, which works great for me.

    Maybe one day out of every 7-10 days I get hungry earlier than usual, so I’ll go ahead and eat earlier. While I’m determined to end my old “grazing” habit, true hunger is there for a reason, so I’ll feed it. Forcing myself to go hungry is just a stupid punishment, and counterproductive.

    I did try alternate day fasting, and it was not a good method for me; consistently keeping the 18/6 schedule every single day is far less stressful than the alt-day “rollercoaster.” And while I used to do a “cheat day” followed by an extended fast day in order to deal with cravings, I don’t bother any more–the cheats made me feel like such crap, I no longer crave that stuff. So the cheat days (which raised a lot of eyebrows) turned out to be a useful tool.

    Calories do matter in my case, and IF has given me an easy way to restrict calories without having to count them (which just triggers a lot of old anger and self-loathing for me). There really is only so much I can eat in my 6-hour window before I’m fully satisfied, and it typically comes out to around 1400-1600 calories.

    Weight loss has been slow but steady since I started IF. But since I’m comfortable with this way of eating, I think it’s sustainable for the long term.

  64. I have been doing IF for a few months now and I have found it to be excellent. I was already primal for a few months and I had made the switch to fat burning beast, and it was very easy. I have had no problems, and great results with fat loss. Most of my friends would definitely struggle do go any length of time without food – carb addicts! My motto is if IF feels easy then I fast (normally miss breakfast) but if it starts feeling hard I stop for a while. Thanks Mark, love your work.

  65. Okay, now that I’ve got my anecdata out of the way, a couple of thoughts about the studies cited above:

    I’m always skeptical of rat studies when applied to humans. And in this case, I’m skeptical for the simple reason that we don’t think like rats do, and there is a mind-body connection that is completely ignored here.

    Ms. Ratty, when deprived of food, has no idea when she’s going to eat next. If there is no food, there is, as far as her little rat-mind is concerned, NO FOOD. It is a crisis. So her behavioral and physiological responses will reflect this crisis.

    A woman (like me) who is intentionally fasting for any length of time knows that plenty of food is available. She knows where it is, and knows that she will definitely be able to eat soon. Thus, she can manage stress that might arise from not eating in ways a rat cannot. And you can’t tell me this doesn’t also have an effect on the body’s physiological response.

    When it comes to the human studies, what I want to know is this: what were the subjects eating when they did eat? Were they fat-burning, keto-adapted folk? Or were they sugar-burners?

    Because there’s no way I could have done IF like this, much less alt-day fasting, as a sugar-burner. I would have been incredibly stressed out the whole time. There’s a good reason Mark and others emphasize waiting until you’re fully keto-adapted before trying IF–it’s just too bloody awful if you’re not.

  66. I don’t fast, but I have found that eating three squares instead of grazing keeps me from thinking about food all the time. For me, that’s as much of a change as a person who is used to three squares and cuts down to two. It’s very liberating not to have to carry snacks wherever I go.

    Perhaps fasting differences from person to person are a matter of degree, not a matter of kind.

  67. I understood IF to be a random period of going without food- and for me it worked nicely with the new experience of forgetting to eat once I went primalish. It seems many here planned and scheduled IF rather than going with the flow of body signals and had neutral or bad results. Perhaps the key is listening to those signals- feeling satiated and energetic? Maybe that’s a good time to pull meal skip- that’s how I’ve done and I can feel it burning fat stores. The best part though is it has taught me how to control mIndless eating and cravings.

    I don’t know- just thoughts

  68. I’m a 57-year-old woman toward the end (hopefully) of menopause. I started with Atkins a year ago this month and discovered MDA and primal about 6 months ago. I haven’t lost fast, but I am losing. 50 pounds so far, with maybe another 15-20 to go. I’m diabetic, so true IF is not something I would be able to do. However, I am able to go longer between meals without being hungry and without having low blood sugar. I no longer have to carry glucose tablets with me since I’m off the sugar/carb roller coaster. No more crazy highs, no more scary lows. Last year this time I was on three diabetes meds twice a day. Now I’m taking one med once a day. That’s a huge difference for me.

  69. I am a 32-year-old woman, and I started doing IF back in February. I started because I wasn’t losing weight even after nine months of strict Primal eating and exercising. My IF regimen is to skip dinner on Tuesday and Thursday, and lunch on Saturdays and Sundays, for a total of four skipped meals per week. I’m careful to keep my other meals the same size as they were prior to IF.

    IF seems to be working for me. I’ve lost 10 pounds since February, with no ill effects, except some mild mid-fast grumpiness. (My husband and I fast together, and we tend to bicker on Tuesday and Thursday evenings, and midday on the weekends. Coincidence?…Definitely not.) My cycles, energy level, and moods when not fasting haven’t changed. The few instances of the mid-fast munchies followed less-than-Primal eating. I learned that I need to prioritize protein in the meals I do eat in order not to be constantly jonesing for a snack when fasting.

    In short, I’m optimistic that IF will help me continue to lose excess fat. I hope Mark’s post doesn’t deter women from trying IF. If I had read this post back in February, I might not have tried it, but I’m so glad did.

  70. When I was a student, I fasted regularly as a spiritual discipline. Two non-consecutive days a week, no food or caloric beverages at all during the entire day, which probably made them about 36-hour fasts. I was eating well, although not primally (little processed food, moderate carbs) and my body adapted very well, to the point that I stopped being hungry on those days at all and actually welcomed the break from having to eat. I don’t remember any adverse effects at all.

    During my pre-primal weight loss (about 60 pounds), I experimented with the mini-meal method (didn’t like it) and settled into a rhythm of not eating breakfast until I was hungry, which sometimes meant missing it altogether. I found I lost weight better that way than the often-advised method of eating first thing in the morning to kickstart your metabolism. I still function that way. If I wake up genuinely hungry, I eat right away, otherwise I wait. I don’t push it, because I have CFS and I don’t want to introduce extra stressors. And I’m in no hurry to lose at this point, so 2-3 pounds a month is just fine.

    Thanks for this post, Mark. I think your attitude of proceed carefully and find out what works for you is a wise one. Having said that, I would very much welcome a little research into paleo for menopausal women. I have heard that after menopause, a woman’s body will actively convert muscle into fat in the interests of maintaining estrogen levels. Clearly, the metabolic issues here are vastly different than for a young men. Judging from the forum journals, older women in particular are having a very different experience at least as far as weight loss is concerned. There is some anecdotal evidence that a certain deliberate carb intake actually favours weight loss, and that even younger women experience hair loss and other adverse effects from going VLC. I do understand that you are not a researcher yourself, but these are questions worthy of further attention.

    1. Ah, I forgot to say that men who fast should give their food to me.

  71. I had to chuckle with the IF and chemotherapy study. I had breast cancer eight years ago and underwent six months of chemo. I guess you could say I fasted…I was so freaking nauseous I absolutely could not eat. I’m fairly certain most oncologists would not recommend IF for their chemo patients, as they are more concerned about them staying well-nourished when nausea and vomiting are so common. Malnutrition is a major concern for these patients.

  72. I’ve been IFing for about a year (Im 25), although not strictly until recently. I aim for 14 hours overnight, sometimes more or less obviously. I actually didn’t notice any menstrual problems until I started going really low carb.

  73. I had surgical menopause at age 37 so I may not be a good one to comment on this. I’m definitely post-menopausal – because (don’t laugh) I’m 77 years old now. Living in Hawaii does have its rewards! I’m in great health, doing IF keeps my weight where it should be, blood work still stuns my physician because it’s insanely normal. I love the Primal way of life, not sure I could go back to any other way. I’m full-time faculty in a college and even my students are amazed at my energy. Age 107, here I come!

  74. I am 34 year old female, 5’9″ tall, 150-155lbs and fat adapted. I fast anywhere from 16 to 36 hours every 1.5 weeks… or just when it happens. I simply like breaking the cycle of eating times and the pull food can have on people. I have had lunch dates with people when I was “fasting” and just said that is what I was doing and had water or tea. It opens eyes to the idea that you do not have to be controlled by food or conventional eating times. I also love running while fasted and never lack energy or get hungry, even if I do a 10 miler at the end of a 24 hour fast. So many people mistake thirst for hunger and I think fasting has helped me get in tune with my body. It also allows you to really taste the complexity of your food when you break a fast. I would like to lose 8 pounds but they just seem to want to stick around! I am never hungry or low energy, probably because of that 8 pounds. It really is all about what works for you and makes you feel good and appreciate life.

  75. I am a 45 year ild woman. I do a 36 hour and a 24 hour fast each week. I haven’t noticed.any problems with mentrual.cycle changes ir sleeping.
    My osoriasis.has cleared up. I have been IFing for about 5 months and have lost about 12 lbs and at least 4% body fat.
    I am now relatively lean (about 22% bf).

    It seems to be working well for me and I have no trouble at all sticking to the fast.

    Stefani’s article does give me pause however and wonder if I am doing some long term damage.

  76. I am still in the process of losing unwanted body fat. I am fat adapted and have started a type of intermittent fasting. I have broth that I make from every other day and eat my regular primal meal when I’m not fasting which gives me acquitted fat and protein and about 50-100 carbohydrates a day depending on my mood. As a woman who is per-menopausal, but I’d say 70-80 lbs over weight I think IF might be the thing for me. Granted I don’t know if you could call it a true fast since I an drinking broth and if, I am truly hungry I’m just going to eat. However, so far it has been great it broke my 3 month plateau and has simplified my days.

  77. I got into IF inadvertently — started drinking “bulletproof coffee” (coffee + butter + coconut oil) first thing in the morning and wasn’t hungry until 1pm.

    Did it for a few weeks. Felt great, better than ever, looked really healthy at around 20.5% body fat, BUT ran into a problem when I went to donate blood … turns out my iron levels were really low. They said if I donated blood that day, they’d have to turn around and give me a transfusion!

    I’d been primal for over a year and never had a problem with iron levels before when I went to donate, no doubt because I was eating red meat or fish a couple times a day, plus a few eggs & maybe bacon for breakfast.

    But doing IF meant only one red meat meal a day (the other was eggs) *and* eating less overall because I felt full sooner, so my intake of red meat was way down.
    I never would have known I had a deficiency — the nurse asked if I was tired, e.g. found it difficult to go up stairs, etc. But, on the contrary, I’d gone out for an hour & a half run that morning, just because I had lots of energy and felt like it and still felt fine.

    I did notice that I would go to sleep a lot earlier some nights…. so, overall my experience was that under conditions of IF, my primal body was using/partitioning my decreased resources pretty efficiently. Which makes evolutionary sense, that once when fat adapted we could still function well with a variable food supply.

    I’ve gone off IF for a while, for obvious reasons, while I re-adjust my iron levels. When I do go back to it, I’ll ease off on the fat so I eat more meat calories and continue the mineral supplementation I’ve started.

    It is amazing looking back on the year of being primal without IF or mineral supplementation, that I didn’t have an iron deficiency despite having a 23 day cycle (yep, every 23 days) and donating blood every eight weeks.

    It does explain why when I choose my meat, I always want red meat and nothing else!

    1. bullet proof coffee wow that’s something I’ve got to try!!!

  78. IF works for me. I’m 48, have lost 40 pounds in the last 6 months and after years of being perimenopausal (early onset due to pain and stress, I believe) am back to having periods. Damn. I thought I was done with that. This time last year I was biking 50-70 miles per week (chronic cardio) and trying to lose weight by eating healthy whole grains, veggies and fruit. Instead of losing weight I was slowly gaining. I started by going wheat and sugar free and have found my way to mostly Primal. I IF most days, but not all days and not on a schedule. I love the freedom of not having to be in the kitchen all the time, pack a lunch, etc. I eat lots when I’m hungry and enjoy it immensely. My pain levels have decreased and I’m trying like hell to regrow cartilage with lots of bone broth and IF for healing. Thanks for the website, Mark.

  79. Thanks for this post Mark. It seems like almost every time you post something about female-specific issues, I learn a little more about why I don’t get fantastic results from my dietary efforts. I’ve got a very broken AND female metabolism. I’ll probably never be robustly healthy, let alone look good naked, but at least I’m finding out why. The more I find out, the less I feel like a failure.

  80. I’m 49 and have been Primal for about 18 months now.

    Once I got fat-adapted (about 3 months in), I had no problem with daily 16/8 IF. It’s still my preference; generally I eat from 10-6.

    I can comfortably do 20/4 occasionally, but my one-time 40 hour fast brought my normally regular period on 5 days early.

  81. I’m a 44 yo post-hysterectomy woman who has been living primally for 18 months now. I find that when the weather is good and I have physical work to do I just don’t want or need to eat during daylight hours most days. If I try to work on a full stomach I just can’t do it. Some days, however, I get really hungry mid-morning so, if there’s no heavy work to be done I just eat until I’m full. I’ve maintained a pretty constant body shape for a year now although I do notice better defined muscles during IF periods. Works for me I guess.

  82. I have been wondering for a while if IF causes some kind of stressor on my body. Personally, if I fast too often, I may feel good but then I start to get a cold sore/irritation on my lip. Odd, because I didn’t even remember even getting them since sometime around high school.

    My bestie and partner in Paleo/Primal pursuits also has noted that she picked up a rather yucky cold just as she was completing a fast. Again, another nod in the “stressor” direction as we are both pretty freaking healthy these days!

    FYI, we are both in late 30’s, no meno yet!, and have been eating Primal/Paleo for about a year or more. We’ve been experimenting with IF as a solution to the stubborn fat or “last 5 lbs.”

    I am wondering though, if IF isn’t the best solution for SOME folks for that last few pounds, what are some other options?

    Love the posts and all the copious amounts of info we find here! Best regards from WA.
    Sheryl

  83. I am a 43 year old woman and I have been IF’ing for about two months and eating primal for 5 months. I had been dieting for nearly a year when things evolved into primal eating.

    Primal was the first lightbulb. I can eat what I want within these parameters (no grains, sugar, etc.) and I am no longer food obsessed. I eat and am satisfied and I lost some more weight.

    IF was the second lightbulb. I do a 16/8 fast and don’t eat breakfast, but eat WHEN. But the main thing that I have learned from IF is that I can say no to any type of food anytime. IF has totally freed me from food controlling me.

    I don’t have periods (hyst. 8 years ago). But I feel great. Plenty of energy, good mood, sleeping well. I’m still about 25 pounds above my “ideal” weight, but I am 82 pounds down from my all time high, so I’ll take it.

    IF on!

  84. It’s definitely a case of ‘what works for you’.
    I’m a daily 16/8 faster, and my wife is a daily 14/8 faster. Whilst I’m happy to do it year-round, this doesn’t always work for the Mrs.
    At certain ‘times of the month’ and during other periods of ‘life-induced stress’, fasting becomes difficult (hunger pangs, mood swings etc) and I often recommend that she avoids it altogether during these times. Like you say, why add yet another ‘stress’?
    So thanks for your post Mark, it does validate some of the patterns that the women in my life already seem to be following 🙂

    C.

  85. 37F with PCOS paleo for ~70days almost 30lbs lost recently hit a plateau. I am 5’10” and obese.

    I’ve been fasting by accident for a couple of weeks and this week I decided to actually track it and try the bulletproof approach… mostly b/c of all the hub-bub about women and fasting and b/c I am just not as hungry as I used to be.

    So far I can report that I feel pretty awesome. I noticed that I don’t need as much sleep and I’m super alert at work but that could be the coffee in the morning. I’m not hungry until well into the afternoon and don’t feel any energy slow downs. The last month I had my first regular non-medication induced cycle in ….. well in years. I am not trying to conceive so I’m not that worried about fertility but I do wish to be “regular” and I also am hoping to cross the plateau and lose more weight. I am eager to see how this goes and will decide in a week if I want to continue.

  86. Every single person is different when it comes down to nitty gritty details, there is no one way to live day to day that works identically for everyone.

    I haven’t had the opportunity to try IF while fat-adapted, yet. I’m not totally sure I’m fat-adapted right this minute (but I’m actively working on it). I’m 22 with regular everything and I own two dogs. Does IF affect premenopausal women with dogs differently than premenopausal women with pet fish? Probably.

    I’ve spent too much of my short life trying to find the magical formula for weight loss, and I’ve never been more sure that there are few constants in the search for health. I’m a premedical student and I’m choosing to make my life a quest to bring health to as many people as I possibly can, and I’m already researching the biochemical and physiological aspects of the different approaches to wellness. Once you get to eating real, whole foods that are minimally processed and as free of chemical additives as possible, and are consuming enough fat for good cell turnover and energy and just enough carbohydrates to fuel your lifestyle, everything else is up in the air…

    Fasting. No fasting. Water fasting. Juice fasting. No grains. Soaked grains. Gluten free. Raw food. Cooked food. Vegan. Vegetarian. Primal. Paleo. Dairy. No dairy. Calories. Carbs. No carbs. Fermented. Red wine. Chocolate. No red wine or chocolate (who does that, seriously?)

    I think we need to disable the instant dogmatic response, stop arguing about who’s right, and start working together to see the benefits of all these things and recognize that everyone has a different winning lottery number for their own nutritional needs, and what foods will nourish their bodies and souls.

  87. HAHAHA,
    Nice to see a younger response (no offense meant to the non-20-somethings on here)…

    I’m 24 yr old female and have been primal for 2 yrs. I have found fasting to be problematic for me. The only exception is if i fast and immediately exercise upon waking, I have a well adjusted appetite for the day, and can manage cravings if they arise. Otherwise, fasting leads to mood swings, cravings I didn’t have before, insomnia, and is damn near impossible during my cycle.

    Chances are, if you’re a woman in your 20’s, you work too much (especially if you’re trying to afford primal), sleep too little, and have a lot going on in different directions. Maybe fasting isn’t the best thing?

    1. 29 year old female, here! Went Primal right before my last birthday and I eat when I’m hungry. Sometimes that means skipping a meal, eating it later than usual, or having a light snack instead.

      I have had no adverse side effects and always feel sharp and alert when I IF.

  88. I’m a 26 year old female and after reading Mark’s posts on IF I was surprised to learn that I’ve been IFing for years, even before I adopted the Primal diet. It comes naturally, and I think it may be why I was able to switch over to Primal without the typical carb flu (my body was perhaps already accustomed to slipping into ketosis). When I fast I also tend to be extremely focused–not sure which is cause and effect. Am I fasting because I’m too focused to take a break and eat, or focused because I’m fasting? Either way, I associate fasts with long, productive days and a strange sort of clarity of thought.

  89. I’m a 45 yo female in those wonderful years leading up to menopause. I’ve also got issues with hypothyroid and adrenal fatigue.
    I’ve been 80/20 primal for a couple years. I can go months strict primal, then a blip and I’m on sugar for a while, then get back to strict primal. I sleep well for the most part.
    I’ve done fasts over the weekends with BP coffee, did OK, even did a 5 day fast, got through it fine. Second time I tried a 5 day fast, body went into not sleeping, being cold constantly. While it cleaned out some really old cholesterol out of my liver, not worth doing again until I can afford the GTA, Isocort and other meds.

  90. Lordy this is what I love about Mark – not taking a firm stance on “I’M RIGHT YOU’RE WRONG RABBLE RABBLE RABBLE”, but instead looking at all available evidence, and making a rational decision based on the evidence at hand. Even if that means changing a previous inference you thought correct. It’s such a practical, rational stance, and I wish more people of influence took note. Regardless of the subject matter (although this is INCREDIBLY interesting!) it’s just so refreshing to have someone not take being wrong personally, and not hang onto their preconceived notions with every ounce of strength, regardless of all evidence in the face of the contrary.

    Thank you, Mark, for continually helping me learn.

  91. My experience with 3 months of fasting the fast 5 way with a 80% primal diet was very negative…the adrenaline surges were great in th beginning for energy boosts but just this weekend I triggered into blood sugar so low I was hospitalized for critically low potassium levels. That was only 3 months…and now my adrenals are so burnt out that when my blood sugar gets low I trigger a panic attack. It has been 3 days now since the hospitalization and I’m eating low sodium (high sodium creates adrenaline) and a more balanced carb/fat/protein ratio. For me, moderation in all things works best for me.

    1. Exactly. I actually need more salt though. Guess we just burnt our bodies out in different ways. Without enough salt and too much potassium I get heart palpitations and really low blood pressure.

  92. I’m already lean, 47 yrs old, and I have never felt good fasting for more than 12-15 hrs unless I am down right sick, which is also rare since eating primally. I don’t get light headed and cranky since I cut out grains and increased my fat intake, but when my stomach tells me it needs fed, I get to it.

  93. Recently I have been watching my caloric and carbohydrate intake a lot more closely and have experienced bouts of insomnia from 2am-3:30am every night. My husband gets up for work at 5am out the door at 5:45am, and the baby is up at 7am meaning i probably get around 5.5hrs of sleep a night now.
    This article now has me wondering if its an induced side effect of wheat elimination or if it could be that I’m simply not eating enough and waking in the night for food.
    I walk every afternoon for an hour except sundays (which i usually end up walking anyways because its our beach day), and do strength training 2 days a week and yoga twice a week also…so its definitely not a lack of muscle movement.

  94. Glad to see this article, too! I tried Fast5 (eating in a 5-hour window), found it very difficult. Moreover when I didn’t stick to the window, I started having a HUGE appetite just before bedtime, and ate ton. For me, better to eat more often–when I got away from Fast5 and started eating a late breakfast, my appetite normalized, and it was easier to cut out the night-time eating.

  95. I’m a 53 year young post-menopausal woman and I IF randomly when I get caught somewhere late and have to skip a meal. I’m fat adapted and it poses me no problems.

    I don’t really know if or how it might be helping me, except that before going paleo I would NEVER have been able to skip a meal. Now I can with no suffering.

  96. I am a female, 35 years old. I have beenof weight and felt great! Then six months Primal for a year and a half, lost a lot ago I came across Leangains website and decided to try IF (along with the weight lifting I was already doing) as I was very interested in obtaining a super lean physique (yes, I want the six pack abs!). I jumped into a 16/8 eating routine and immediately (within 30 days) lost my period. I had always been regular before that. I stuck with the IF routine for about 4 months and I did loose bodyfat and maintain muscle as was my goal, but at what cost to my hormones? I can’t say I physically felt any better on IF. After reading up on the negative effects of amenorrhea I am very concerned for my health and very much want my hormones to be regular again. I stopped daily IF about a month ago but have seen no changes regarding my now non existent cycle. I definitely want to put out a word of caution to younger, already lean women who are thinking about IF. I really think it pushed my body over the edge regarding hormone balance and I wish I would have read Stephani’s blog before trying it. Thanks Stephani for getting the word out.

    1. Whoa, sorry, not sure what happened to the beginning of my post there. It should say… “I am female, 35 years old. I have been Primal for a year and a half and lost a lot of weight and felt great! Then six months ago I came across Leangains website…”

    2. God. So many of us have experienced similar issues, but I have simply never seen it addressed before; we struggled alone. I agree with you; wish I knew then what I know now. Good luck to us both eh?

  97. I’ve been Paleo now for about 3 months, and IF happens randomly for me. Some days I’m just not hungry, and I’ll go 8-10 hours before I get hungry, then I’ll eat a small meal so I don’t shock my system. I’ve noticed on days I fast that I sleep better, and the next day feel much more energetic with better concentration. On days I fast I usually don’t do anything crazy like a big hike or heavy lifting.

  98. hi, I am a 28 years old female who planned to have babies in the next2-3 years. I am currently skipping breakfast and start with lunch 12 pm every day and eat dinner around 7-8 pm. I have lost a lot of body fat doing this, from a curvy US size 4 I am know a skinny size 2. I feel great in terms of how I look and my energy during the day is great but I have difficulites sleeping during night time. I am tired and go to bed around 11-12 but do not really sleep unitil later, so I often sleep in during the morning and wake up 10 am. I have always have difficulites getting to sleep but since I started IF T think it got worse. Since I have not feelt tired during the day I have not been concerned by this, but with this article warning about sleeping problems I am scared I am messing with my hormones and won’t be able to get pregnant in 2-3 years. I still have my period and eat a low carb, non-grain, non-diary (except butter), non-sugar diet, with lots of fat (5.5 tablesspon of coconuut oil, 2 tablespooons of butter, + the fat from protein). Should I be concerned and stop IM, I have only done it for 2 months and it fits very naturally with me as of no hunger in the morning, I am not forcing myself at all to stay on this time, and it is so mych eaiser to plan for 2 healhty meals than 3 at the same time it has helped my cravings for carbs and snacking big time. I really want to continue with the IM but if it will compremise my hormones and getting a baby in the future I want to stpo as that is much more important. Can people please give their thoughts?
    Cheers

  99. I’m a woman who, last year, decided to “get healthy” through dietary changes. I was already reasonably lean, just out of shape because I rarely exercised. Anyhow, I adopted a peri-primal diet–that is, almost primal; I still eat small amounts of legumes, oatmeal and quinoa–and I lost a bit of weight. Granted, at the same time, I also incorporated mild to moderate exercise in my daily life.

    To clarify, before my dietary changes, I had largely subsisted on cereal, lowfat plain yogurt, rice cakes, and sugary drinks/candy. I’m in my late 20s, and on the low end of the BMI (~18 to 20; as it fluctuates). I would say that my suspected blood sugar issues (cravings, jitters) seem to be under control since I made these changes.

    Long story short, I stopped menstruating in August of last year. I think I got too lean, though my appearance is not noticeably altered. I have begun to gain back some weight and hope to not need the progesterone recently proscribed to me. I never did any IF, but caloric restriction seems, to me, the culprit–notwithstanding more sinister possibilities (which did not show up on any diagnostic tests). . . . Would love to hear from anyone who experienced something akin to this!

  100. Hi there. I’ve been reading MDA for awhile but this is the first time I’m commenting.  

    I’m 21 years old, 1.63m and 52kg. I’ve been paleo since last December (with some cheating of course), but I started IF last September as a way to burn off excess body fat (especially in the lower-abs). I started off at 52.8kg, dropped all the way to 49.5kg in December and put the rest back on in terms of muscle mass because that’s also when I started bodyweight training. I fast every day for at least 16 hours (Leangains) and train in a fasted state. I push myself quite hard and fasting allows me to not have anything to throw up after training. Most of my daily fasts last more than 16 hours because I only eat one meal a day and I make it a large meal that ranges from 1200-2000 cal. Sometimes I do feel hungry during the day but it’s not a “give me food or I can’t function” kind of hunger that I used to feel before I started IF/paleo. It’s more like “oh, my stomach is empty now”. Fasting has become more of a convenience than weight loss tool for me because it’s almost impossible to find healthy food outside. (I hail from the “Fried Rice Paradise”.) I prefer fasting the whole day when I’m in school and cooking my dinner in the evenings. It’s become a huge part of my lifestyle and I really like how convenient it is. 

    Which is why I’m quite reluctant to admit that I might have to scale down on the way I IF. I do notice that I haven’t been sleeping very well since this May. It may or may not have anything to do with IF but before I read this post I didn’t know that hyperactivity could be caused by fasting. I just thought it was because the “natural” and “original” way humans slept was in two 4-hour sleep cycles, which was kind of what I was experiencing every night. 

    Any males reading this might want to skip to the next paragraph. I still have my period every month, but I notice I don’t bleed as much as before I started fasting. Does anyone else experience this too? I don’t even need to use those super thick overnight pads anymore. On one hand I’m like “oh yay, it’s not so messy now” and on the other hand I wonder if this makes me less fertile, if the next thing I should expect is that my period will stop coming. I do plan to start a family next time, although that will probably be in ten years time. I know I do consume less calories than my daily requirement on some days, but that’s only because I don’t eat (that much) empty calories. Can’t possibly consume more vitamin-packed calories unless I want to eat >500g of veggies, which in my opinion is already quite a lot. I guess it’s not just about the calories, but also the fact that fasting is a stressor to the body. 

    I also find that my appetite varies during different times of the month. I have quite good self-control by now but on some days I just can’t seem to stop eating. (Two nights ago I had 190g of protein in a pretty awesome dinner. Too much?) It’s probably something to do with the hormones during the different times of the month when the body is trying to “build” or “break down”. Anyhow, I fast every day regardless, but this could be a reason why some women might find it difficult to fast – it’s probably the wrong day of the month. 

    So to sum up, this is the healthiest I’ve been in my life which is why I think my paleo/IF lifestyle does suit me, but on the other hand the fertility part kinda worries me. 

    Thank you for reading this extra long comment. 

  101. I feel really good on a 14 -16 hour overnight fast as long as I have coffee when i wake up. I am a 42 yr old female, primal and crossfit for about 5 months. Lately I have been doing crossfit WODs towards the end of that IF and have good workouts and strength sessions. Fat adaptation feels wonderful. I no longer fear missing breakfast or a morning snack and my energy level is good.

  102. 31 yr old woman. I tried fasting but I noticed it triggered overeating and food obsessions. I do 12 hr overnight fasts, maybe 14 at the most without problems, but longer than that and things go awry! This post helps confirm what I had discovered about myself already. I dont feel like a failure now. 🙂

  103. My 9 yr-old daughter enjoys eating the paleo foods we prepare and has noticed and commented that she is not very hungry with this style of eating. She will often go 8 hours without eating if she has eaten a high fat, high protein, lower carb meal. ( but We do not restrict her eating). She is pre-pubescent (thank goodness).

  104. I haven’t gone primal yet. I’ve ordered the books, and they have not yet come through- which is too bad.

    but I’m at the stage in my weight training regime where i’m squatting in the range of 250 pounds, with deadlifts slightly heavier- and squatting and deadlifting at that range tend to take the p*** out of me, if i hven’t fuelled up adequately.

    Admittedly, i’m still a sugar burner(and diabetic to boot-F***). I don’t think it’s the safest thing to IF for me right now. Here’s to hoping things go my way- and i get to give you guys better news soon!

    Mark

  105. I’m a 19-year-old female with PCOS. Before going Primal I had a history of eating disorders – anorexia, bulimia, and compulsive over-eater/binge-eating disorder (they were inter-related, as you can imagine – an evil self-repeating cycle, all in the name of losing weight). I’m proud to say that I’ve conquered anorexia and bulimia, but the binge eating remained. Even after 6 months of eating Primal, I’ve still found myself bingeing on massive amounts of sugar. Part of this is emotional, and I think the other part is that I can’t ever make it to the end of sugar-detox/becoming fully fat-adapted.

    But anyways, that brings me to IF. I’ve found recently that IF is an amazing solution to my binge eating triggers. For the past week I’ve been eating one meal a day – a 1200-1400 calorie lunch (sounds massive but it’s not if you consider how high calorie many delicious fats are :), and then fasting till lunch the next day. It’s working so well for me. It’s sustainable too. The one meal is unbelievably satisfying, and after that I don’t have to think about eating for the rest of the day (one of my biggest problems was after-dinner bingeing). Without dinner, and by carefully planning my meal every day, problem solved!

    This past week alone I’ve lost 8.2 pounds. I know some of that is definitely water weight, but I think it still says a lot. because of PCOS, I’m trying to keep carbs at an absolute minimum (even having any fruit at all makes me crave sugar), so my large meal of the day is usually a 3-egg omelette, cooked in coconut oil with lots of spinach, and either bacon, an avocado or a ground beef patty smothered in olive oil and spices. SO GOOD. But anyways. It keeps me full, energized, and alert for the entire rest of the day. Even my periods have become more regular. It’s been great. I think that IF is potentially a real and lasting solution to my binge eating problems, and in a very different way than anorexia ever was (not worried about slipping into that again). The only bad part is trying to explain to people that you eat one huge meal a day, dripping with fat/saturated fat, and are losing weight. So I’m just holding out until I lose more weight and people start commenting, and they’ll have to believe my explanation 🙂

    And sorry for this absurdly long post. Kudos and thanks to anyone that actually reads all this.

  106. For the first few months I forced myself to eat eggs, bacon and veg for breakfast, and then I just stopped. I wasn’t hungry, Ive always hated breakfast, so it felt right to not eat it.
    I would eat lunch, fish other protein and salad and veg. Dinner more veg/salad and meat.

    About 6mths into my primal journey I stopped losing weight. So I started to not eat on the two days that I worked. (Im at uni the other days).

    My work results (targets) improved, and my end of day balancing (I work in finance) became significantly improved. I felt more switched on, more engaged, more interested in my job.

    I would eat my night time meal and was fairly hungry, but nothing maddening or anything.

    I drink a few coffees when I fast, but mostly green tea.

    Lost more weight, felt better, hair and skin fine. Unsure of menstrual cycle as I don’t get my period (IUD).

    Love fasting. Pretty sure Im fat adapted.

  107. I am a 30 year old female. I lost my period 4 years ago from over exercising and under eating. I have been IF’ing by skipping breakfast for over 2 years. I was diagnosed with hypothalamic amenorrhea in July 2011. I regained my period while IF’ing. For me, the negative hormonal impact is more about taking calories too low than it is about when I eat those calories.

  108. I’m a 37 year old woman with PCOS and severe insulin resistance. I also have IBS(D) with SIBO.

    I’ve never had a problem with hunger, so naturally seemed to eat in a 5-8 hour window when I started low carbing. I had huge problems losing weight, even on low calories, low carb, high fat, despite being really obese. I decided to try eating just one meal a day, and slowly I am now losing weight. I am also having far less sugar cravings and my digestive issues are much easier to handle. I also feel better eating this way – and noticeably worse on the odd days that I have eaten more than one meal.

    I’m not typical though, in that I’m pretty broken, and probably need this dramatic action to begin to correct the damage. I suspect I have large insulin surges in response to meals – even when just protein and fat (evidenced by the fact that my blood glucose drops after eating, it doesn’t rise). I believe that eating one meal a day has reduced my total insulin output enough to be able to (slowly) access my fat stores.

    1. What does SIBO stand for?
      And I’m with you, I only eat once a day too and feel great.

      I randomly check my blood sugar levels and it’s all over the place. Even after 2 months sugar free I was still in the 100s from fasting.

      Before going paleo I was hungry all the time. Now I can go hours and hours without hunger. I find it frustrating to explain this to other people who insist that I must eat every so many hours. I just don’t think we’re all made the same and we have to find what works for us…. like you I’m obese and I definitely felt broken but I feel like I’m mending.

      1. Sibo stands for Small Intestinal Bacterial Overgrowth – basically I have nausea, bloating, pain and all food tends to go straight through me.

        I too get shock from people when I say I normally eat once a day – they insist I must get dizzy and have unhealthily low blood sugar. They also accuse me of starving myself and being anorexic – but I eat about 1800 calories a day in my one meal (plenty of fat included), and just drink water the rest of the day.

        Hopefully this regime will mend me too!

        1. I was diagnosed with SIBO last year. I won’t get into details, but my only symptom was…messy…and seemingly constant.

          Anyway, I was put on antibiotics for 2 weeks, then was told to “wait and see” if my symptoms returned. They did. So, I was put back on the antibiotics for a YEAR. “Are you sure this will work this time?” “It has not failed, yet.”

          Well, I was very unhappy because not only was I taking a drug for a year, but it did not seem to start working consistently again until I had only 2 months left!

          Then I went Primal.

          And all my symptoms VANISHED. I finished the antibiotic and am still symptom free. All is well (and regular). So now I wonder if it was the SIBO or just the SAD diet that was my problem.

  109. I have a two year old and a six month old (who still wakes every 2-3 hours for food, even though he’s been eating things like egg yolk, meat–chewed by me, sweet potato, etc), so if you include pregnancy, I’m working on a year worth of sleep deprivation/never fulfilling a sleep cycle. I started IFing intentionally after reading Mark’s post to see if it would help me lose fat (190lbs on a 5’6″ frame…down from 220), even though I’m still nursing. Anyway, I gained 10lbs back (went from 180 to 190 and fluctuate within a couple pounds of that every day), and I find myself eating massive amounts of food at the one or two meals I eat a day (kids days directly impact my ability to eat). Carb (sugar) cravings increased dramatically, I’d wake up starving at 3 or 4 in the morning, get headeaches, etc. Obviously, due to weight, constant stress (no sleep plus two kids on my own usually 24/7), and not being fat adapted means no intentionally IFing for me. Too much stress on my body as it is.

  110. I’m pre-menopausal and very lean. I tried one 24-hour fast (water only) just to see how my body would react, and I didn’t like it. I did fine, which is amazing in itself, since I couldn’t imagine going more than 4 hours without food in my pre-primal life, but I didn’t feel awesome. By the end of it I was headachy and a bit grumpy. So I don’t do those anymore, and I think 12-16 hours is probably my limit for a comfortable fast. I don’t do them on purpose, but if I don’t have time or appropriate food I frequently skip lunch and find that I can handle that with no problem. I’m continuing to lean out and build muscle, so it doesn’t seem to be causing me to gain weight. Every now and then a longer interval without food will give me a headache, but that’s considerably less distressing than the symptoms I used to get from being hungry.

  111. I’m a 64 yr old female; postmenopausal & on hormones. I can fast between 12-15 hours and that’s about it. I don’t do it often though. I find it difficult to do more than once a week.

  112. for Marks “study” purposes: 53 YO PM female. When I first went primal, I seemed to “effortlessly” (its always an effort for me – but weight was consistent for 3-4 years) be able to maintain a very lean 132, about 20 bmi, 15% (VERY correctly measured DEXA) body fat. Over the past year, my weight has creeped up. My hypothesis is that the scarcity signals are overwhelming what was already an intentional hormetic way of eating, as I gain/maintain weight at my theoretic/calculate lose a pound a week level. I added the IFing for 18 to 24 hour periods, and intensified training with greater emphasis on Tabata-style. I like the cold water swimming, but by the temporary increase in blood glucose, I suspect it is also fairly stressful.My body temp really seemed too low (rarely/never at 98.6), so now I’m tracking to better understand what impacts it. Because I’m always playing with so many variables, its a little hard to say what causes what, so I’m trying to really focus on quantifying as many measurements as possible. It may be as simple as just eating more calories:-). I am using Cronometer to try to keep myself honest, but it is pretty easy to be in “denial.” That it was a tsp of fat vs. a tablespoon, etc.

  113. I’ve been contemplating a more basic question: should we ever go hungry, and if so, how much? I am a 35 year old woman, breastfeeding a 7 month old (she just started on solid foods, but nursing is her main source of calories and nutrition.) I haven’t tried IF per-se (and won’t while nursing), but I have expanded my time between meals, and sometimes when I wait to eat until hungry, then have to actually prepare something, plus take care of 2 small children, it starts to feel like a fast. (Especially with food intolerances to convenient foods like eggs, dairy and nuts.) I’ve been losing weight fairly rapidly (1 or 2 lbs/week). I still have 10 or 15 to go, but I’m super happy to be 17 lbs BELOW my pre-pregnancy weight. Just wondering if occasional hunger is spurring weight loss, or if it will eventually slow my metabolism down. I think I am “fat-adapted” and have been eating primal/paleo for about 10 months, and gluten free for a year before that.

  114. I have been experimenting with fasting the past year with great success. I have been coaching people using fasting as well. I can say from experience that for me fasting next to paleo has been the most positive change in my life for health and fitness. It allows me to eat massive and I mean MASSIVE meals while “dieting”. You can check out my results on this site actually as Mark posted my success story. Most of the women I do coach and advise have a much harder time with fasting then men. I recommend most do a shorter fast window of 10-12 hrs rather then the 14-16 I do my self. I train fasted and have gained muscle while losing body fat pretty easily. I do think it is a great tool if you love skipping breakfast and eating huge meals but I know alot of people men and women who love breakfast and like smaller meals and try to force themselves into fasting. Its supposed to make your life easier not harder : )

  115. I am a 42 year old peri-menopausal woman who started the primal journey at 185 pounds (5’7″) and is now 143 pounds. I’m not wired for breakfast. I’m just not hungry until 10 am or later, so occasionally skipping dinner and then eating a late breakfast worked well in the beginning for energy level and fat loss. Now at the lower end of my weight, I notice that I feel weak and spacey. This also depends upon where I am in my cycle and how much protein intake I’ve had that week. I suspect that I have some adrenal fatigue, like a lot of folks. If this were balanced, fasting might feel better. The most important thing is to simply pay attention to your body.

  116. I found this post discouraging, because I’m trying to fast each day til late afternoon, then eat. I tended to binge when I tried this the first time for a couple weeks approx. Not from hunger, but from food obsession. I’ve always had the food obsession, so that is one big plus for fasting during the day. It eliminates that obsession, and I don’t feel hunger. It eliminates thinking about food, making decisions about food, etc. A HUGE plus for me.

    I’m 55 and female and postmenopausal. I also have the apple- shaped body, which is more male-like, if I understand it correctly. I stopped trying to fast for awhile and have now started again. This time I plan to mostly eat Paleo/Primal. I’m trying to lose 10-15 lbs., but my main concern is health.

  117. This is timely as I am working my way up to doing a fast. First thing I tried was skipping breakfast if I wasn’t hungry.I realised how I had bought into the idea that you have to have brekkie and basically you have to eat every few hours or you will go into starvation mode. Thinking about that now, if that were true it would make humans very inefficient and unable to achieve much as they would have to stop to eat every few hours or – in theory – wake up in the night to eat.Sometimes I get up for work at 5am and I cannot face eating so I have enjoyed just waiting to see when I actually get hungry. At the moment I have not eaten for over ten hours. I’m not sure if I’m hungry!
    I always seem to get very hungry just before my period and during the first few days of it. Like I will feel like I am going to keel over. Last time I had this I had to have a Coke, nothing else would do, and I felt miles better.

  118. I am female 5’6″ 130lb (lost 56lb 2.5yrs ago), 67yrs, so definitely post-menopausal.

    I naturally lean to IF as I’m rarely hungry in the morning. Husband and I have almost finished a whole 30 and can’t wait to get back to our normal pattern which is a coffee with 2 tblsp coconut milk shortly after we get up. Around 1pm we stop for lunch which is usually a huge mixed salad with a protein, either sardines or other fish, meat, eggs, whatever we fancy on the day. Dinner is usually around 6-6.30pm and is mostly cooked vegetables, 4-6 different ones, and a protein. I have fruit to finish off my meals. Doing it this way works well for me and I rarely get hunger pangs. If I do feel hungry in between I will have a snack, maybe some jerky or fruit or nuts. I try to eat only when hungry. I have great energy but still not a consistently good sleep pattern. But that has been so for many years so I don’t worry about it.

  119. I’m 42 and still fertile. I went Paleo about 10 months ago while in the midst of losing weight. Since going Paleo, I began to plateau, but that may simply be due to the fact that I’m down to the last 8 lbs and that’s never a quick loss. I started doing IF (and P90X) about 5 weeks ago. It’s been easy. I have definitely noticed the whole more-alert-and-energized thing, and thankfully have not had a problem with insomnia. But I’m happy to have read this post so I will know what’s up if this problem should appear. The IF has not really worked as a plateau-busting technique so far. On the other hand, I’ve gone from a size 6 down to a size 2. So it’s definitely doing something for me!

    In addition, IF has turned out to be a fantastic tool for confronting and exploring my food-related anxiety and control issues. Even if it winds up not working as a weight loss tool at all, it would be well worth it for that alone.

  120. I’m 44 years old with no sign of perimenopause. I have extremely regular periods which have become PMS-free since going Primal 2 years ago. Even as a kid, breakfast was revolting to me. I had zero appetite until midday.

    For the last 20 years I’ve fasted most days 14-16 hours without thinking of it, just following my hunger. Typically this means I have a tiny lunch and a big dinner. The difference with Primal eating is hunger is just a sensation. It’s not accompanied by a sudden drop in blood sugar and focus. On Primal I can fast and function very steadily for 24+ hours although I prefer not to. Eating is pleasant.

    If I add weight training on top of my physically demanding job (building contractor) my comfortable fasting period is on the shorter end. Ideal weight seems to be connected to finding the carb intake sweet spot – not too much, not to little. Also weight training. Just going Primal didn’t help me loose that extra 20 pounds, although it did help a lot of other things like injury recovery time and mental function.

  121. I typically don’t eat first thing and always train on an empty stomach. However, my experiment with IF proved disastrous.

    I am female and in my 40s (I was around 42 when I attempted this, am 45 now), healthy and not on any medication. I tried the Warrior Diet-style IF, eating only in the evenings, and actually gained 10lbs during the process. My body temp dropped during the day and I felt cold (not a good sign) and felt sluggish, not alert.

    I eventually lost the weight using a protein shake diet (not something I’d recommend, but I was desperate).

    Since then I don’t IF consciously. If I happen to miss meals for various reasons, I don’t sweat it and my body copes pretty well. But the whole eating once a day thing definitely didn’t work for me.

  122. 20 yr old overweight female here.

    I can only IF if it comes naturally – i.e. I’m not hungry and just decide not to eat. If I do it that way, I don’t suffer any ill effects from what I’ve noticed.
    If I try to plan a fast, or do it any longer than say 20 hours, things usually turn to crap.

    I saw the post a few weeks ago about IF’ing and women so I have actually already done quite a bit of thinking about it. Thanks for writing about it Mark

  123. Lots of great thoughts on the subject of fasting. I have just found like some others on here that it diminishes my exercise experience. Even exercise that is more incidental to fun (rather than a program regimen). That down side is too much for me to do it. Can’t say that some of what people are saying on here hasn’t made me reconsider that position though. That is one of the beauties of this site.

  124. Reading the comments I find it a bit of a shame that I didn’t try IF after starting primal but before I started hormone treatment.

    Personally I find that when I IF I become obsessed with food. But I also find it a useful tool to reset my brain and body when I start to eat off track.

  125. I have been experimenting with 24-60 hr coffee and tea fasts with some remarkable results, thus far. There are still minor carb craving issues near the end, but those are eliminated more and more as triggers are discovered.
    IF is an extremely useful tool, and perhaps a minor crutch–albeit a sound one.

  126. 38 yo female, 5’10”, 150 lbs +- 10 lbs for the past 20 years. Former marathoner, primal (including exercise protocol) for 2 years.
    I practiced non-structured IF for the past year. (I ate only when hungry). This evolved into a feeding window of noon-7 pm most days, where the noon feeding was very light, working up to a good hearty (primal) dinner. I had never felt so good in my life! If primal food wasn’t available, I could go all day without eating and experience no discomfort. If I was particularly enjoying a certain meal, I would indulge a bit and eat a bit more than I probably needed. If I woke up hungry (rare) I would start eating earlier in the day. It all balanced out.
    Then I became pregnant and everything is out of whack. I don’t get hungry, but if I don’t eat every few hours I feel terrible. So now I am eating by the clock rather than by appetite and I feel all messed up diet-wise. I don’t enjoy food anymore because I am rarely hungry due to eating so frequently (hunger is the best seasoning).

    I will be interested to see how this all plays out and if I return to my previous patterns after baby.

  127. I’m 52 female peri?menopausal. I started 16/8 IFing about two months ago. I’ve leaned out even though I haven’t lost lbs. My energy and moods are good. Our 15yo granddaughter came to live with us last month = stress.
    My period has been regular; about 28-29 day cycle but last month I went 47 days between periods.
    I notice that I wake up at 3am and have trouble getting back to sleep. I was thinking that maybe it was just a normal primal split sleep pattern that Mark describes. Hearing about other women waking at 3am with IFing has me thinking that it’s time to experiment a little to determine what is true for me.
    Thanks to Mark and Stefani for sparking the conversation and to all that shared their experience.

  128. I am 32, female, 5’8″, 145 (just happily put on 10 pounds in the past few months with a muscle-mass/strength-building program), the most regular periods ever (no birth control) and have enjoyed occasional IF, while eating mostly Paleo (definitely no grain, little sugar) the rest of the time. I tend to do 16-19 hours once a week or so and have had the same results of stable energy levels, and improvements in workouts — I actually tried IF as a way to shake a sort of rut/plateau in lifting. I especially like Mark’s comment about fasting when you need to — I’d rather do an unplanned fast than eat the unhealthy and overpriced offerings at the airport, for example.

  129. THANK YOU for this slap around the head – truly; I needed it.

    IF has *not* been working for me, and yet for some stupid reason I persevered. Why? I like not bothering with food during the day, find hunger manageable, and, if I’m honest, have spent many years fighting a perfectly healthy set point (160lbs at 5’10”, weight training, above average lbm) by always attempting to keep calories as low as possible. Stupid.

    I have gained fat, and lost my cycle. Hormonal mess, clearly. There have been life stressors also – but still. Just because one *can* do something does not mean one should. IF is utterly wrong for me … and apparently this message has finally sunk in. Thank you both.

  130. Thanks so much for this post. I’m still a newbie to Paleo (coming up on one month)and I was never able to play around with IF before switching to Paleo, as I would get “the shakes” if I went too long without food and then I’d struggle not to binge. Since I started following a Paleo diet, I’ve been able to do short fasts for the first time. Ever. I’ve just dipped my toes into the water – skipping a lunch here, eating an early dinner and not eating again until late the next morning. But it was big for me, and I didn’t struggle, feel fatigued, hungry, or moody. Your blog has been a big motivator for me.

    Then I stumbled across Stephani’s blog post and was confused, and a little discouraged. Reading your post and the responses to it have helped me decide to continue playing around with it, while listening closely to my body.

    Thanks so much for all you do!

  131. I’ve always alluded to the fact that women hormonally cant sustain on low carb. Ive written on my experience while IFing for 8-10 hrs, it would be stress inducing for my mind to relax and fall asleep. My first time going paleo, i lost my menstrual period for nearly five months, rough time getting any sleep which lead to late night food cravings, lost a lot head hair, grew more FACIAL hair, would get facial redness and drastic puffiness. The second i upped my carbs, my period returned. I will even admit i was much more healthier on a 80-20 vegetarian (but still wheatfree) diet than low carb. Men and womens sugar fasting levels are entirely different.

  132. I can’t do the IF thing either, and I’ve been Primal for over three years now. I’m 29 years old, 5’9″ and weigh 120 give or take a few pounds. I can skip breakfast once in a while, sure, delay meals because I’m not hungry, but I only made it 24 hours a couple times with some serious willpower on my part. Usually I hit about 18 and I’m like, “Good enough, where’s the food?!?!” I get lethargic, cranky, unmotivated, and hyper-focused on my next meal. As in, I’ll count down the hours until I’m allowed to eat. I don’t really think that’s the spirit of IF.

    Like some others have said, I’ll use it as a tool when I’m traveling, but that’s about it. I’m pretty active, I’ve always been underweight with a high metabolism, and I tend to prefer eating small meals that don’t leave me feeling ridiculously full.

  133. I am 42 and can go for a 14 hour fast easily. 16 hours is a bit of a strech, but i can pull it of. I never fast voluntarily though, by following a plan or deciding it beforehand. I let it occur when it occurs naturally (It´s the WHEN method, I guess.)
    I never had any problems in skipping meals, quite on the contrary: it always makes me feel wonderful during the “fast” and also after breaking it.
    Planned fasts never worked for me. Not eating when I am hungry is a total trainwreck, physically and emotionally.
    To put it primally: if I am hungry and can´t get food, I have no problem in lifting (and tossing) heavy things! 😀

  134. Despite Stefani’s suggestions, I myself am an avid fan of IF. I’m a 26 yr old female, 5′ 6″, 118 and have had digestive issues my whole life. IF really helps mitigate most these issues (as well as living a paleo diet / lifestyle), but I have to say that IF is the icing on the cake. No hormonal issues or missed periods, in fact my body is more in tune with itself than it’s ever been. Definitely agree that it is good to self-experiment, do one’s research, etc. but Mr. Sisson your insight has been a big improvement on my own personal health and well being. Thank you!

  135. What IF does is takes one away from obsession with food…..if this is done regularly, like everything else, the body memory kicks in and says ok, now i can divert my energy to other activities beyond digestion…
    Unless one has a medical condition.

  136. Dear Mark,

    Paleo for Women blog says that fasting may not be for women: that it’s more suited for male physiology. I have been fasting for three years and never experienced any missed periods/sleeplessness, etc. Moreover I got a handle on my mindless eating. Can you give your word on IF for women?

    Varsha Tiwary

    =

    fasting month for muslim is coming up in 17 days. women or non women we have to fast. more than a billion women

  137. Hey all, I study fasting and wrote this up for another website. Here’s a blurb I wrote on why fasting doesn’t work that well for some normal women:

    “Women already have elevated levels of IL-10/adiponectin, which is the main advantage that arises from IF. Naturally the values of Apn/IL-10 vary from girl to girl, and I’m guessing this is why some women would benefit while others would suffer (IL-10-Apn-AMPK-HO1 act in a positive feedback loop during fasting, and the levels of each increase proportionally as you fast). Here’s the catch though, women have shit Apn sensitivity because their serum values are consistently higher than male counterparts so their tissues develop resistance to it by decreasing the amount of Apn receptors (think insulin resistance, behaves in a similar way). So if you fast and just increase your already high serum numbers of Apn, you’ll just increase your resistance to Apn, and bam, that’s why you see fat gain and all the metabolic disregulation when normal sized ladies fast (Apn resistance is also a late stage phenomenon in advanced Type II diabetics). This doesn’t mean fasting sucks for all women, just women that have a “womenly” IL-10/Apn profile.

    And that’s why, as a women, you need to f#@%ing weightlift to take advantage of it. Resistance training is the only thing proven to increase Apn receptor levels and sensitivity. “

  138. I haven’t tried fasting–just not snacking feels like liberty to me, and I do get hungry at mealtimes. I’m only 6 months primal but I’ve been a low carb type 2 diabetic for going on 8 years. I have always eaten a little carb before I exercise, even at 5:30 am, because I had read that fasting exercise on top of the dawn effect can lead to higher and higher bg as the liver releases glucose but there isn’t enough insulin for the body to use it. Eating a small amount of carb is supposed to jump start the body to release insulin.

    I read that years ago–I have no idea where or whether it is still current. I think what I will do is take my blood glucose meter to the pool and test every half hour through a swim workout while fasting and see if it does work that way for me.

  139. I started eating primally in March, 2012 – I know I am new at this. I have not deviated from the lifestyle at all in that time, and feel at this point, I am a fat-burning beast! I have no cravings, and feel so good physically that I cannot imagine going back to consuming wheat or grains.

    I have lost 20 pounds (still have a way to go). I am peri-menopausal, 55 years old. I do IF once a week, usually with a 20 hour fast. I have had no difficulty with sleeping, hunger or general weirdness. Fasting allows me to be reflective and increases my clarity.

    That said, as previous authors have stated, the success of IF and primal eating depends on the individual’s response to it. Try it, listen to your body, reflect on how you feel, and carry on! Thanks, Mark for all you do!

  140. I am 36 year old female who stuggled with blood sugar in younger years. IF and weight training has been great for me. I listen to my body and don’t schedule the events. If I am not hungry I don’t eat breakfast. Weight training and running intervals are no problem. I have found I sleep better and have great energy on those days. Normal work outs are 30 to 40 minutes of intense training.

  141. Hello Mark,

    I am a 51 year old female and I was able to successfully do intermittent fasting last year to lose weight. I also did a sort of warrior fast for a couple of months except my meal was a normal sized meal (not particularly large). I sort of stumbled into it was not really “planned” but it worked for me.

    Now that I’m approximately 10% body fat fasting is a bit too hard on me. I can get through a fast easily enough but I tend to want to eat up everything in the house afterwards and that just does not feel healthy to me, so I don’t do it.

    Three years ago I was in the obese catogory; I’m 5’1″ and I was 171 lbs. I was very physically active have been for almost 31 years.

    I’d tried most every diet out there over the last 15 years and lost and gained. I finally got tired of it along with the slow weight creep up year after year. I started eating my own diet, simply healthy foods I like in small portions. I put my meals on small desert plates and typically had 2-3 small meals a day and maybe one snack. I followed a rule of not eating past 7pm and then gradually set that time earlier, say 5pm or 3pm only because I felt I had enough calories for the day. Without planning on it I did “mini fasts” for 15-17 hours which was interesting because I never fasted before in my life. I lost 40 lbs this way. I told a friend one day that I thought I found the secret to weight loss; mini-fasts and mini-meals. He told me to look up “eat stop eat”. That is where I found Brad Pilon’s intermittent fasting book which I purchased (along with the women’s workout Venus Index which I LOVE).

    So, I tried out a 24 hour fast and found it quite rough. I could not complete it the first time. I felt dizzy and nauseous and thought well this isn’t for me. I tried it again a week later and was successful. Then I did this once a week no problem, then twice a week. I followed the program as Brad described eating a normal sized meal after my fast.

    Then for some reason I got excited about this and started doing a 24 hour fast nearly every day for about two months. I didn’t plan to do this. I would simply wake up in the morning and decide that I felt like doing it again. I probably had a couple of days where I had more of an eating window or switched it up because of a social event that involved eating.

    Typically I did a lunch to lunch fast and did a fairly long gym workout each afternoon (taking one or two rest days a week as needed). My workouts were 1.5-2.5 hours depending on my energy level which was usually pretty good and my workout included 1-1.5 hours of resistance training and .5 to 1 hour of running, depending on how I felt. Sometimes I would skip the cardio depending on DOMS, constantly listening to my body and what I needed.

    I lost an additional 17 lbs during the three months after I started Eat Stop Eat. But then I hit a wall and for the first time in my life felt like binging and didn’t like the feeling one bit. I did went and got a hydro-static body fat test done at this point and found I was at 10%.

    I’ve maintained around this lean level for almost a year now and through a few fasting experiments found it is not so good for me anymore. But it isn’t really necessary anymore either since the point is not to go to 0% BF!

    While I did the fasting I found it worked best to only do it “when I felt like it”, sort of going with the flow of my hunger hormone cycles. Forcing it because of a “plan” for the week does not work for me.

    That was my experience with intermittent fasting.

    -Roberta

  142. Started fasting daily and I love it. I’m a 23 year old athletic female. I eat about 2000 cals in a 5 hour window. (I’m a monster I know..) and feel satisfied until the next day. I started with a bigger eating window at first. And my workouts suffered the first 3 days. But now I am so much stronger and have tons of energy throughout the day. I can do way more chin ups and push ups than before. I Sleep like a baby I am way less moody and finally didn’t pms this month. I don’t think I can go back to eating small meals. My mood has just been far too good. Please keep us ladies updated on IF for women.

  143. I suspect the level of testosterone matters. It varies from woman to woman. I think I have more than average as I put on muscle quickly. And I have no problem with IF, it worked great for me as a weight loss tool and my body adapted readily to it.

    I think men vs women is too broad of a categorization, as there is a lot of variation among women.

  144. Thought I’d share my story…….. I’m a fit 37 YO and I found intermittent fasting pretty easy for the first few weeks and had lots of energy. i was doing a daily 16-18 hour fast and eating between 1200-1600 kcal/day. being 5’2″ I figured this was enough calories even though i do pretty heavy lifting 2-3 times/week and HIIT 2-3/week and have a lot of muscle mass. Well, after a few weeks I began to wake up ravenously hungry every morning (totally new for me) and find myself dizzy, low energy and grouchy by mid morning. then I began having obsessive food thoughts and cravings for treats. i eat a pretty clean paleo diet and never got below 17% body fat, but lost my period within 6 weeks of this program. clearly i need more calories and/or more regular meals!

  145. Hi there,
    I am a 33 year old female athlete who has incorporated IF into my life since March of this year. I follow a 16/8 daily and also do one 24 hour a week. I mainly stick to lots of veggies and meat as well as fresh fruit (though usually only following a workout) so you could say that I am “fat-adapted”. I love IF. It has done wonders for me! I am 5’6″ tall and weigh 176 lbs and am about 18-19% body fat. IF has brought me to numbers I have never seen before in the gym ( 200lb bench press! 300 lb dead lift! 15 wide grip pull ups, while still maintaining a 25 min 5km run!!). It also has really helped in leaning me out. I can literally feel my body breaking down the adipose tissue in my abdominal area ( a real trouble spot for me!). Many other people have commented on my shape changing (I don’t notice it that much because I am constantly looking for results) But the best of all, I have constant energy throughout the day and that is very important as I am a partial-insomniac!! I do not crave food like I used to….when I am truly hungry, I know it. IF has also allowed me to identify a gluten sensitivity that I couldn’t nail down before. I recommend at least trying it, but remember it works best if you are fat adapted- if you stuff your face with pasta and bread for 8 hours, don’t expect to not be hungry for the remaining 16….your body loves carbs as it is an “easy” fuel,. Give yourself a chance and ease off on the carbs before you try IF… I think you will find it a lot easier to adjust. It took me about 3 days and then I just wasn’t thinking about food anymore!! I recommend it to all athletes! It is not difficult to maintain at all…I just get up, don’t eat, go to work and then eat lunch, back to work, hit the gym, come home and eat! Simple! Good luck everyone!
    Thanks!

  146. I am female, 54, post-menopause. I fast for about twenty or twenty-one hours on weekdays, entirely for the sake of convenience. I’m not an early-morning person, no matter what time I go to bed, and I have a long commute, so I don’t like to spend morning time cooking and eating breakfast.

    I habitually work through the lunch period, because that’s a productive time of day for me, though I do have business lunches once in a while (not a problem, I always have plenty of appetite for free food).

    My main, or only, meal starts around 8 or 9 in the evening.

    At weekends, I have two meals a day, brunch and my usual late supper. I eat a high-fat, moderate-protein, low-carb diet on average (I think I eat 60 to 100g of carbs per day).

    I feel well on this regime, but it does *not* work for losing weight, and I am slightly overweight (BMI 26).

  147. Mark, I am a 35 year old female and have been doing IF. I usually do a 16/8 or a 20/5, and I feel great. I walk 4-5 miles a day (briskly) in a fasted state and lift weights several times a week. I was eating “healthy” and excercising but not losing the 15 lbs. I could never get rid of, so I tried IF and have finally been able to see results. Plus, I feel a lot calmer overall (less stress and anxiety) and realized I was obsessed with calorie counting and meal times before. IF has allowed me to be in tune with my body’s needs abd finally see results. My menstral cycle has not been affected nor has my sex drive. Thank you for your web site. It encourages me and gives me the necessary knowledge to get fit and lean plus feel better!

  148. I have just starting IF, and I am fasting breakfast each morning and waiting until I’m actually hungry, around lunchtime instead of automatically eating breakfast first thing, the way I have done my whole life. I am also trialling fasting each Monday. This has been good (and easy)for me, but this week I tried a 2 day fast and woke up this morning (day 3) feeling absolutely terrible – weak and nauseous. I had a healthy breakfast and lunch and I’m starting to feel better now. I think a full one-day fast per week, and daily breakfast-skipping fasts are what works best for me. My body was certainly telling me off this morning! I lost 2kg in two days, which is probably a bit much! I only have a couple of kg’s to lose for my ideal weight anyway – only 1 more to go now!

  149. Well id like to be able to fast, being a 25 years old female. But starving myself like that sends me into a panic, I just can’t do it. I previously suffered from Anorexia Nervosa and I associate food restriction with purposefully starving myself, so whenever I attempt to fast I find my body going into more than just a panic, it thinks Im ging to starve it again.

    Maybe in future I can bring fasting into it, but for now its too soon after the illness.
    H

  150. Eating one meal a day has worked for me when nothing else would. And when I switched the timing of that one meal from midnight (I work late) to noon, I got even better results. It’s taken 3 years, but I’ve gone from 165 (where I’d been all of my adult life) to 130 lbs. I’m 5’7″ and age 57 and just got my first bikini!

    I’m one of those who never gets hungry so this is a winner for me.

    Another help was doing 8 sets of sprints on my elliptical every other morning.

    Interesting side-note: I never quit drinking, but switched from wine to vodka and stevia-sweetened lemon juice.

    I can’t do weight-training due to arthritic joints, but I’m lookin’ good! LOL. I get more attention now than ever before in my life–matronly, not for me!

    Sometimes it all comes down to switching stuff around and seeing what works for YOU.

  151. Oh, and I have a physically-demanding job too. Mark, I wish you’d write something about those kinds of jobs since many of us are not sedentary office workers, and how that fits the Paleo lifestyle.

  152. I was wondering if diet drinks are allowed during IF? Thanks. Also can I use sweetener is my tea/other drinks? Thanks.

  153. This is probably a dead thread, but I just found it.

    I don’t know if anyone has mentioned this, but if you want to do a large study on women and fasting, you should do it during women who fast during Ramadan.

    During the month of Ramadan, Muslims abstain from food and drink (not required in IF) from sun up until sun down. My husband’s entire family has done this their whole lives with the kids starting around the age of 6. None of them report any of the effects Stephani is talking about (which doesn’t mean they’re not really happening).

    I’ve done it and the only problem I have is that I work and I can’t stay up all night to eat, so I end up not getting enough calories and I have trouble not drinking any water during the day. However, beyond that, I don’t have any other problems as a woman. I’ve done this fasting in my 20’s and 40’s.

    The point is, if you want to know what happens to women when they fast for a relatively long period, studying women fasting for Ramadan is probably a good idea.

  154. Benn doing IF for 5 years…no problems. One thing I must say is when I go from 2 meals a day to one meal a dya during my periods I gained less weight at this time and the weight that I did gain came of easily post menses.

  155. I’m a post-menopausal female, and a few years ago, I tried IF. After maybe 24 hours without food, I broke my fast and kicked off a lovely week-long bout of intense gallbladder pain and vomiting. It took a few months to return to normal, and I’ve been careful not to fast more than 12 hours or so since.

  156. Very interesting comments above and of course great article by Mark.

    As for me, I am a 28 year old female tipping the scale at 112 pounds. I did the IF for two weeks. I ate in an 8 hour window and fasted 16 hours. My results…

    I ALWAYS felt hungry, my body never really adopted. I gained about 3 pounds on the fast (not my intent). My goal was to help my body the proper rest from digesting all the food I ate. I was hoping I would feel more alert, be in a better mood, and increase my weights while I lift in the gym. I didn’t see any difference.

    I am back to eating my first meal around 8 or 9am and eating my last meal around 5 or 6pm. I might sneak a small bite of chocolate around 8pm but very rarely. I feel way better and focused on this schedule. I eat three large meals and 1 snack in the middle of the day.

    The results for IF is all over the board. I’d say, give it a try and if you like the result then go for it. If not, then you didn’t sign a contract with Satan so go back to your normal routine.

    1. So you went from an 8 hr feeding window to a 9 hr feeding window? how is that much different.

  157. I would just like to represent myself. I have been primal for about 2 months. I am 25 and probably very fertile, and whenever I think about fasting, I can feel my body saying NOOOOOOOO. Some inner voice is telling me it would create stress, at least at this point in my life. Besides, I have lost 20lbs and am still losing, so I guess I don’t see the point of IF.

  158. Hi Mark! Great article, thank you for your well-researched content. Back in Feb I followed a daily 14/10 IF protocol in conjunction with heavy lifting for 30-days. As you can imagine, it stressed my body to the point of hormonal dysregulation and has required significant time to recover from. Although I’ll never partake in this particular method of IF, I still occasionally enjoy a 14-18hr fast. I love the science behind IFing and am still very curious about the differences experienced by men and women. Again, thanks for the great information! Keep it coming

  159. all i wanna know is if the differences are psychological or physiological. i would hate to gain weight on IF!
    if it was psychological it could just be that many women are apparently conditioned to turn to food as their comfort – versus if there are actual hormonal differences then that can’t be helped i guess

    i want to lose about 10 to 15 pounds and maintain it. i’m pretty sure i have a high metabolism so this is my first attempt in my 20 years at dieting but why not go for the best – and IF does sound like the best!

  160. I did 16/8 daily fasting for about 6 months, tried 20/4 fasting for 6 months, tried a 3 day fast once (would not do it again) and have been doing IF now twice a week for 24 hours at a time for about 2 months. I have GI issues (a physician recently called it mind-gut, also acid reflux, and other things).

    IF has helped quite a bit. I find it much less stressful than dieting. That’s why I find it interesting that there were stress symptoms in women who fasted. I think some people psych themselves out thinking that IF isn’t healthy! Some people freak out and think they’re going to die or something without a day of food, or they have some disorder. My boundaries are that I never fast for more than 24 hours, once or twice a week, never two days in a row, and I end the fast when I get true hunger at any point. IF makes perfect sense to me and I like the break for my system. Not only do I save big on grocery bills but also it opens up a lot of time during the day and my nights become more efficient. I’ve lost 35 pounds in the past 2 years and the scale keeps dropping. I have 20 to go and will continue with IF, pilates, yoga, and biking and see where it all takes me. Good luck in your own journey. Like everyone else said, listen to your body!

  161. Anybody out there female, middle-aged, menopausal? I’ve been doing IF for about a month now, and have tried several permutations — 2 consec days/wk; two split days/wk, 3 split days/wk — and half lost 1/2 stone (7lbs). I also workout 4 hours a wk, including interval training, free weights and calisthenics. I’ve noticed astounding muscle gain (it really IS remarkable!), but last week I had a hormonal meltdown. Like PMSx400%. Severe seratonin drop; felt suicidal, weak — high cortisol, extremely irritable, and massive migraine. Although the headache has now receded and I’ve recovered from the emotional drop, I remain extremely fatigued. Any ideas from anyone? Should I stop? What might be causing this? Should I go on with modifications? If so, what sort? Any ideas welcome. I’d really like to go on with fasting –I’m losing the weight around my middle, looking younger and building muscle. As well, occasionally I feel better than I have in years.

    And then, occasionally, I feel worse than I ever have in my life, except postpartum.

  162. Dear all,

    I am a 36-year old woman. Today I finalized Fasting as recommended by Dr. Med. Hellmut Luetzner.
    Fasting according to Dr. Luetzner is a 8 day program during which I strictly did not eat for full 5 days (day 2 to 6). The first day of the program was to get the body and mind into fasting mode, I was allowed to eat raw fruit, veg and nuts; the second to sixth day consisted of tea, tea and even more tea, a glass of juice, and half liter of veg broth. During the last two days, you can eat things like a proper soup with veg in it, some fruit etc. I was motivated throughout the program, however I have to admit that I felt increasingly dizzy and physically weak; mentally I had tons of energy. I was able to concentrate for hours, hardly needed any sleep, and was in a really good mood; usually I get angry easily and I am very impatient, however during the IF I was really calm and at ease. Today I was finally able to take a bite again, and I am feeling miserable. After every tiny bite of food, I need to find the nearest toilet to vomit. I already ate twice today, with the same end result.
    I had fasted before, around 7 to 8 years ago, and I remember that I had tons of energy to spare, however I did not have any difficulties.
    The aim of fasting was to detox my body. As a positive side effect, i lost only 1.8kg this time, and around 5kg last time.
    Hope this helps.

  163. I’ve been trying intermittent fasting for two weeks now, and find myself stuck in a psychological rut at the minute unfortunately. When I put my head to fasting I can REALLY do it, and dont find it that hard,and find myself feeling little pangs of joy/self pride in the middle of the fasts at my progress, and generally more appreciation for what it actually means to be hungry. Hpwever the last two weekends ive let myself have a treat at the end of a fast because of unavoidable occassions and the junk calorific food that generally accompanies such occasions. And… it just went out of control! 1 “treat” turned into 36 hours of bingeing (im talking alcohol, pizza, chocolate cake and chips to name but a few) It’s like the minute i let myself taste a little bit of indulgence i CANT stop. this switch turns on in my head and i dont stop unitl i feel physically sick to the very core from stuffing my face. the first time i followed it with a 36 hour fast and felt a bit better about it. this time, i dont want to do such a long fast b/c i want to do work over the wkend and need energy for it…. but i just want advice on how to get out of this cycle of successful fasting/ healthy eating and savage eating because i have at least a stone and a half to lose before my GW is reached. Please offer any advice its really getting me down.

  164. I find this interesting.

    I have been doing a variation of IF, I suppose. I am 23, female. I do not do well with long fasts, I will literally eat anything and everything that is not nailed down when it is over (and maybe some things that are nailed down.)

    I have been waking up in the morning, having green tea, working out without any food in my belly, then waiting between 2-3 hours to eat my first meal. WORKS LIKE A CHARM

    My body fat percentage has just been falling. My appetite is decreased, and my energy is increased.

    For any women, or men for that matter, who do not do well with long fasts- give this a try. It’s wonderful..

  165. Hi, here’s my story. I am a 54 year old female. I have been doing IF for exactly one year. I generally fast 3-4 days a week. 18-20 hour fast with 4-6 hour eating window. I work out 2x week with heavy weights. I am 5’6″ tall and have gone from 151 lbs at start of IF to 135 lbs today. Body fat percentage has gone from 24% to 21%. I have lots of energy during the day and I sleep well at night. I will continue to eat like this for the rest of my life.

  166. I fast intermittently. And I do it regularly (about 1-3 times a week). It’s come naturally to me, and the pounds keep flying off. I am however, not active, but I’ve dropped 30lbs so far without much difficulty.

    I keep my calories relatively low, and eat a clean diet on the days that I am not fasting.

  167. 36 yo female, changed from plant based to paleo 3 months ago. I already ate a very clean, high veg diet but adding protein and removing the rest of the gluten free grains has drastically improved my digestion and energy level. I have just started playing with IF because I have 10 stubborn lbs to lose (18 month old baby) body fat is 19.5%, but all in my hips! Would weight lifting combined with IF make it more effective…any resources that you can point me to?

  168. Hi, I’m 5’3, 120lbs. I gained 20 lbs;-(! Help! I need to lose 20lbs to fit back into my clothes.grrr. I’m confused. Which is better, a water fast or IFing? If I fast while drinking water alone, will I lose a lot of muscle??? I read an article saying I should do a water fast for 2 weeks to acheive my goal. I believe the master cleanse(lemon, cayenne pepper and maple syrup) and juice fasting is a bad idea, due to carb and surgar content(I also did both, no offense to blueprint cleanse,lol). I suppose pricy juice fasts are advantageous for people who are already at their goal weight…

    Help!!!!!!!!!!!!

    1. Hey Lauren, first of all don’t worry. Lots of stressing about food can actually put your body into emergency mode and make you store fat and gain weight. I have tried a water fast and IF. A water fast can be very intense and most suggest having supervision if you are going to do more than 3 days. You pretty much need to stay at home and rest non-stop, and also you very well may not be able to think straight, so even working from home or getting projects done may not be feasible. I only did 3 days and I won’t ever do it again. IF gives me better results and I don’t feel weak or have to interrupt my life. It’s pretty simple. Only drink water for 24 hours twice a week, never twice in a row. You can eat every day if you plan it correctly. My husband and I eat dinner from 6-7pm the night before the fast, then eat again at 7pm after the fast. Don’t go under 7000-8400 net calories a week (add calories for exercise). Your body will eat it’s own muscle if you fast for more than 24 hours or under eat calorie wise. I don’t think the master cleanse is a good idea either. Juice fasts are not my thing for the same reason, you give your body somewhat of a rest but not truly. Good luck, I’ve lost 45 pounds so far and I’m on my way to 15 more.

      1. K, did you lose more weight water fasting? Thanks for your response;-) Lauren

        1. Hi Lauren, no I did not sustain the weight loss with water fasting. I only lost three pounds and gained them right back. I would not recommend it. The vast majority of weight goals can be achieved through diet. My daily food intake consists of 5 servings veggies (3 of those dark leafy vegetables), 3 servings fruit, and protein/fat- always a generous portion of essential fatty acids (hemp every day and then either fish or lean meat for dinner), everything organic, 2-3L water, one hour of low impact cardio (cycling), enough strength exercise to where I get every major muscle group to the point where I cannot do another repitition (yoga/Pilates weekly), 30 minutes sunshine, and probiotic supplements. I used a kitchen scale to measure servings for a while to learn servings and now I can eye ball it. I pretty much cut all dairy and gluten due to allergies and don’t eat processed foods. Bon chance!

    2. Please don’t do a water ONLY fast. Starving yourself with water is not the solution and will lead to over eating later. You can either IF or do PSMF which is a protein sparing modified fast. That’s a day you go very low calorie by only having protein with some fish oil and greens. Typically around 1,000 calories. I would’nt do that for more then one or two days at least and wouldn’t do any kind of exercise those days unless its very early in the fast and something low impact like walking or swimming.

  169. I came across your article after hearing that woman should stick with a 14/10 IF period and wanted to research why this is. I am a 21 year old (obviously premeniposal) female, very active–crossfit 5-6 days a week along with rock climbing/hiking/yoga. I do not know my exact weight or BMI but I believe it is around 140 at 5’4″ and 20%BF.

    I was so curious because I recently started IFing and have LOVED it, but 14 hours seemed really short to me. I generally lean more towards a 16-18 hour fast and always prefer to train fasted; I perform my best and may even say my recovery benefits from it. That could just be the primal eating though :).

    I had eating disorders for years (progression of exercise bilemia to anorexia to binge eating) and have spent the past few years overcoming the psychological and physiological effects. I have only been IFing for a couple months but for the first time food does not control my mind and I eat WHEN.

    So far no negative effects-although I have a hard time sleeping more than 7-8 hours a night (but this is always the case). No need for an afternoon nap nor do I feel foggy. Menstrual cycle normal. I just hope that this IFing isn’t too good to be true!

  170. Last year I went a few weeks of alternate day fasting. Not only did I not lose weight, but after I stopped doing it completely my body gained 10 pounds eating how I normally ate before it. I still have on the extra 10 pounds and my body seems pretty resistant to getting it off. Maybe a 2 day a week fast would have worked instead of every other day, but all I know is that it messed something up for me that I hope can be fixed!

  171. I will say, though, that even though IF doesn’t achieve weight loss for me…fat FASTING does. You all know about a “fat fast”, right? (Dr. Atkins wrote about it in his book)–90 percent fat, 1000 calories a day through 4 to 5 mini meals of macadamia nuts,cream cheese, etc… My body gets lean super quickly doing that but I seem to be annoyed more doing it, maybe because it’s easier to not eat at all. I have been dreading doing it, but I have to do something to get this weight off from IFing!

  172. Oh, I forgot to mention…I just turned 30, mother of 3 (not sure if having babies changes anything but probably, everything seems to matter!) and I’m a size 10 and pear shaped. I have been doing kettle bell swings a couple times a week (30 to 50 swings) and that has made my shape more pear-ish than usual, but that’s for another post.

  173. A little late to the comments here, but I’d like to share my experience because many of the comments above made me feel much less alone and crazy.

    I’ve been a natural IF’er my whole adult life. The minute I got to college, I quit eating breakfast and lunch. College roommate’s slogan for me to this day “she doesn’t eat during daylight.” You cannot imagine the grief I’ve gotten for this. I’ve also always been a natural low carber.

    Yet, I eat when I’m hungry. Yesterday morning, I was super hungry so ate some leftovers at 5 am.

    My “normal” IF is 24 hours, 7 days a week. I’m 45 YO, pre-menopause, 5’7″, about 123 lbs.

    Fascinating, I know. The other two tidbits I’d like to offer are that I’ve realized my parents were pretty similar: Very light breakfast, never ate anything else under dinner. My husband has sort of naturally followed me to eat something smaller mid-morning and then dinner.

    It’s not something I think about. I’ve made my peace with the “social lunch” and eat to be polite. Only to find out I’ve doing something that’s “a thing!”

  174. I have been sooo happy IF’ing. I’ve actually hit a weight that I never could before even on a low carb/high protein diet.

    I realize that I used to do this as a kid – I would never eat in the morning.

    I make sure I don’t eat too much when I break the fast so I don’t get a tummy ache after. Yes, I am a female and I’m glad I didn’t listen to the IF naysayers!

  175. I’m a pre-menopausal woman and I have been losing weight taking the adapted form of 5:2 fasting as advocated by Dr Michael Moseley. I eat 500 calories on 3 days a week (not consecutive) and eat normal ( not binge) the rest but that means classes of wines, desert sometimes and YES allelujah – carbs.

    It is really easy to limit your intake to 500 calories and not feel hungry – there are excellent filling soups that come in at 150 calories a serve, a two egg omelette is about $175, grilled fish and salad is also an option – hell there are lots of options

    And it works for women.

  176. I find that the fat loss from my boobs is accelerated during IF 🙁 compared to regular diet and exercise. Has anyone experienced that?Otherwise its great

  177. I don’t IF intentionally. However, I have noticed a pattern in my own eating habits over the years. I go through periods where I have a very large appetite and want/need to eat a lot (prolly close to 3000 calories a day) and periods where I eat nearly nothing (about 1000 calories a day), one point in college my roommates thought I had developed an eating disorder. I can’t explain why this happens, and I cannot pinpoint when I start my low calorie intake (stress, sleep habits, happiness, etc). I am trying not to sink I to the lows as I am breastfeeding my LO, but it still happens. I think this goes in line with our DNA make up that Mark was talkin about, times where food is scarce, times when food is in abundance.

  178. You wont gain FAT unless you eat too much! If you eat more cals than you burn – in a eating window of the day at 6-12 hours OR if you don’t do IF you eay too many cals at the end of the day you get same result – a cal is a cal! So if any of you gained wieght and in bodyfat at IF you are eating junk when you finally can eat! Then IF isn’t for you if you can’t control it after a fasting period!

  179. I just wanted to add something since I commented a couple times already about having a hard time fasting. I am fairly lean now (under 12% bf) and have been for about a year and a half. Prior to that I had been over weight most of my life and never this lean. I found I could easily fast when I had more body fat. I’ve found that it’s hard when I am lean.

    I think it comes down mainly to the difference between intermittent FASTING and intermittent FEEDING. If you mostly don’t eat, then eat during a small window day after day it’s going to be hard on you and at some point you will feel like crap. I made the mistake of doing this and I was fine until I got lean. I also workout really hard, and long workouts, even though I am not a competitor. I just love both lifting and running… and I mean LOVE both and have for over 30 years.

    If you are a lean athlete and you intermittently FEED (mostly fast) or eat too low for your level of work and leanness, yes you will feel like crap. If you are a lean athlete then you can eat low if you don’t work hard, or you can work hard and not eat low, one or the other and not both.

    Not that there are not other hormone issues for some people but in general I think this is the case.

  180. Hi,
    I’ve been following Mark’s Daily Apple for a few years and went Paleo about 3 years ago. I also had a lot more energy (at first) but about a year ago I noticed my hair was getting much thinner and falling out. It happened really gradually (I didn’t fast, only no carb and practically no sugar ever) so I only noticed it late. I do believe there is a hormonal link, since many high starch vegetables, beans and legumes contain Phytoestrogens, but I came to another conclusion as well. Just for the record, this is a speculation, but it makes sense to me. I started taking Biosil (a product that promotes hairgrowth) and after a little research I found that the main component of this product is Orthosilicic acid (OSA). OSA is found in many plants (vegs, fruits) but the highest concentration is found in grains and beer (which uses grain fermentation). I also noticed I just couldn’t relax anymore, even though I practiced yoga and meditation (maybe going Paleo was affecting my serotonin levels as well?) and my muscle strength decreased (even thoug I ate high quality protein – all organic – daily) I’m now eating grains again but not without soaking them first (I use Sally Fallon’s book, Nourishing Traditions for recepies). There may be more to it than that, but I just wanted to share my story so women are aware that there might be down sides to going totally grain free.
    In any case, I wish to thank Mark for his excellent blog. I refer to it very very often and really love it. Thanks a lot for all the energy you’ve put into this!

  181. For me, fasting once a week isn’t a problem. I actually feel much better 10 hours into a fast than I usually do on a regular eating-day. But I can’t exercise on fasting days, or even if I’ve just skipped a meal immediately before.

    I have noticed with my metabolism that it’s highly sensitive to the amount and type of exercise I do as well – right now I’m weight training every other day, and don’t really get hungry at all, but if I’m weight training or running 6x a week like I usually do, I’m ravenous. If I haven’t worked out at all in three days, a six inch Subway sandwich feels like far too much food and I’m not interested in eating the rest of the day.

  182. For some reason, there is no way to “Reply” to the 41-year-old female pro-fitness model, chef and yoga instructor’s comment about her – in her words – “positive” experience with low calorie intake and fasted training (her “thriving on 6hrs. of sleep, mental clarity and increased ability to multi-task). So my reply is ending up here randomly. But I couldn’t help but have deja vu when reading her experience. Didn’t the study that Mark just quoted state:
    “In female rats:

    Any degree of nutritional stress (fasting or mere caloric restriction) causes increased wakefulness (during the day, when they normally sleep), better cognition (for finding food), hyper alertness, and more energy. In short, female rats become better at finding and acquiring food when they fast, as if their bodies aren’t as well-equipped to deal with the stress of going without food. They also become less fertile, while the males actually become hornier and more fertile (probably to account for the females’ plummeting fertility). Ovary size drops (bad for fertility), adrenal gland size increases (which in rats indicates exposure to chronic stress), and menstrual cycles begin to dysregulate in proportion to the degree of caloric restriction.”

    Umm, Michelle…doesn’t this sound familiar? If you have to do this to yourself to get down to the 8% required to win these events, then perhaps the “fitness” competition should be more aptly named…

    Being in the “fitness” industry myself, I tire of the increasing disconnect that is happening between the world of fitness and the world of health. “Fitness” has become more and more about fitting into a certain look, no matter the consequence to your health. Unfortunately, the vast majority of people don’t see this.

  183. Hi guys,

    I apologise if this has already been asked and answered, I did try searching but couldn’t come up with anything.

    I’m trying out the Eat Stop Eat method of fasting (24hrs once or twice a week) and was just wondering whether it is advisable to fast for 24hrs during your period?

    It seems to me that it wouldn’t be a good idea due to the blood/iron loss and general grumpiness that accompanies menstruation, but is there any actual data on this? How do the rest of you approach it?

    Cheers,

    Emma

  184. I’ve always considered myself an IF dropout. I have a seriously difficult time going beyond 10am without eating. I’ve tried 5:2, and IF. I get that hyper-alert thing going where I can’t settle down and concentrate. I know that hunger comes and goes, so I can wait out the hunger pangs, but I can’t fix the restlessness.

    I never really lost weight or saw major differences in my blood sugar either.

    Am I fat adapted? I have been low carb for about 10 years, but I’m not someone who produces a lot of ketones.

    I am 54 years old and finally into menopause, or post-meno.

    To be fair, I think there’s something wrong with me metabolically. I have extreme difficulty losing weight.

  185. Chiming in to say I started IF a few weeks ago after watching the Mosley/BBC documentary. (5:2 – 2x a week, 500cal dinner only. I drink loads of green and herbal teas thru the day until then, then right before dinner I usually make a cup of organic broth just for something savoury. My boyfriend has much less to lose but was curious to try it to improve muscle definition in his abdomen (the only place he needed to really lose anything). In the evening, I prepare a 500 calorie meal, always lowcarb (tonight for instance was spinach, tomato and cucumber salad with balsalmic dressing and grilled halloumi), and my SO has his with extra crispbreads or portions to add the additional 100 for men.

    As for me, I’d previously lost about 21kg (50ish pounds, I believe?) over two years of what I’d say was lowcarb/primarily paleo eating (I say “primarily” because I did continue to eat organic yoghurt almost daily and relied on the odd Atkins bar when in a bind)….but weight loss had stalled after 21kgs, and I have felt – even though I’ve kept it off – that I needed to shake things up a bit. I also felt I was eating healthy calories overall, but still too many of them. (I don’t eat junk food and I rarely touch sugar or wheat – but calorically its easy for me to get too many, since many beneficial foods that I rely on – coconut oil, macadamia nuts for instance – are not exactly low-calorie. I take a few supplements daily (based on the Jaminets’ “Perfect Health” recs – Vitamin D and K2, a B complex, a probiotic, Magnesium, Copper, etc).

    Still – I feel these choices laid a good foundation for IF, because I don’t have issues with blood sugar “crashes”, headaches, I sleep very well if not better since I started this…..so when I see irritability/headaches/blood sugar crashes being described by people for whom it’s not working, I would only question if that could be in part due to nutritional deficiencies or bad diets.

    I see a few stories now and then about people who experienced some issues like this – but then in the same story talk about the gorging on “feed” days, describe junky or carby meals, etc – and I have to wonder if IF has gotten a bad rap when in truth, other factors can be the root cause. I feel like my body isn’t needing anything because nutritionally, I’ve given it what it needs and fuel-wise, it’s already fat-adjusted and not seeking carbs for a quick fix.

    Of course, we’re all different, and I know what works for one won’t for another – but I for one find the research compelling not just for weight loss but improving quality of life as we age and as long as I’m feeling better on it, and feeling my body streamline somewhat, I’m all for it.

    For my part I’m in my 40s, have about 13kg (30 lbs or so?) left to lose and IF has, at least so far, been not that hard at all.

    For what it’s worth, my 2p/tips:

    I deliberately choose my 2 busiest days to fast until the small dinner meal, Tues and Thurs

    I keep lots of herbal and green teas around to enjoy through the day – helps me stay hydrated, keeps my taste buds entertained.

    I have a cup of 5cal broth before the evening meal, takes that edge off if I’m hungry so I don’t eat too quickly, and it tastes surprisingly good.

    On my “feeding” days I make an effort to eat normally and I actually use an app to track calories even on THOSE days so I am sure I have a “feel” for what my suggested goals actually amounts to.

    on Wednesday and Saturdays, we opt for more indulgent foods but keep the day’s food within an 8 hr window and usually just have 2 meals that day.

  186. I stumbled across this website looking for answers because i started fasting last month one day a week and I’m talking real fasting, so nothing for 24-36hrs; one weekend i did 48 hrs and i’ve been doing it for spiritual reasons as well as im trying to lose 5 lbs BUT im now 1 week late with my cycle. I know im eating enough about 2000 cal/average on regular days and i workout 5x/week averaging around 35miles a week. I’m hoping that my cycle goes back to normal since this is a new change for my body. I really like the benefits of fasting so i was hoping to find some reassurance that my cycle will return to normal eventually..I don’t want to stop..lol

  187. I am 51, female, postmenopausal (hysterectomy at 41…still have ovaries). I tried fasting recently for the first time. I was 115 lbs and 5’4″-pretty lean already since I am well-muscled from climbing a lot. I’ve always disliked eating first thing in the morning (though I usually wake up early and alert). I’m totally fat adapted, eating 70 percent fat, 15 protein and 15 carbs. I can workout easily with no food all day, and-like Mark-do so when I feel like it. Also I have IBS and do poorly with solid food first thing. So typically I have about 400 calories of heavy cream when I arise at 6 a.m. ish and then eat eggs and/or meat about 10 a.m. By eliminating the cream I was able to extend my fast from 10 to 14 hours daily. I tried this out of curiousity and also because I wanted to get just a bit leaner as an advantage climbing. (On my 11d project, all one’s weight is hanging from the tiniest little edges in the rock…it’s finger tendon intensive and strength to weight ratio is critical.) What I found was I quickly and easily lost 5 lbs and at 110lbs I have nicer definition in my abs. I haven’t made progress on the climbing project due to a shoulder injury but my IBS was much improved. I suspect this is due to consuming much less cream… the cream has some lactose, which worsens my IBS. But I can tolerate cream and any food better after a longer fast-if I force food too early, when I’m not hungry…diarrhea. I noticed no other changes from this form of fasting. So now I’m holding steady at 110, consuming less cream early in the day and more beef later and just deciding each day, cream in my tea…or not. I like knowing I have this tool to lean out when I want to, and the insight gained on managing my IBS.

    1. Thanks for your post. I am 58, post meno as well. I have been fasting after dinner and not eating anything until lunch the next day. I have a cup or two of coffee with GF butter and coconut oil (1 TBS of each blended w/ coffee in the blender) and have been happy with that. I’m going to see about getting fat adapted and find out what is involved or if I’m close already. I like the idea of eating one or two times a day. I just need to add in some exercise somehow. I think that I will have to get up at 4 to fit it in, I’m a bit “done” when I’m finished feeding the family after work so bed is calling my name by then, wake and start over at 5…. maybe I can just NOT sleep that last hour and do something then.

  188. I’m 39, over weight, mostly primal – feel great when avoiding grains etc. Since March been fasting 2 or 3 days (not a complete fast normally 600 odd kcals in the day) I can now do a full kettlecise class of an hour with nothing in the “tank”(which inc. warmup/ stretches after) and happily feel great afterwards! Don’t really feel hungry till 1pm ish

    But the biggest thing is that my 8 day monthly has changed to 5 days !

  189. What about Blood Type? I’m on the Eat Right For Your Type Diet, I’m an O-Hunter, which means I eat meat. I’ve been doing IF with much success. I do a 36 hour fast on Wednesday and a 24 hour fast on Fridays. Been losing weight on this regime.

    I wonder how fasting plays into this type of diet.

  190. I am absolutely horrified that there are 70+ studies on IF in men, and yet absolutely ZERO studies done on reproductive-aged women. How can all those scientists have completely forgotten to study women? Such an extreme gender bias is mind-boggling.

    Well, I think it’s time for action. There needs to be legislation in place that forces scientists to study equal numbers of women. If women are not represented in studies, then it’s going to flow down as poorer health for women. We can’t accept that.

    Similarly, when the media (Hi Mark!) report these kinds of findings, they need to specify that it’s not yet applicable to humans on the whole, because the studies only looked at men.

    IF is being touted as a godsend and cure-all, when we actually have no idea how it affects over 50% of the population because nobody has done the studies. And apparently, before Stefani brought it up, nobody even noticed…

  191. The following three studies show that regular mealtimes (basically the opposite of IF-ing) improved insulin sensitivity in women. Regular mealtimes also improved postprandial glucose and lipid profiles. Having breakfast, instead of skipping it as many IFer’s do, had similar beneficial effects. In general, there were very positive results for women having small, regular mealtimes and not skipping meals.

    When you add this information to the fact that one study found IF did NOT improve insulin sensitivity in women, AND actually worsened their glucose tolerance, and you’ve got some pretty interesting evidence to be going on with. Obviously, fasting has vastly different effects on men vs women. We can’t assume that what’s good for one will be good for the other.

    These studies are small and sparse, and more research is needed, but the indication is that small regular meals, including breakfast, may possibly be better for women’s health than IF.

    http://ajcn.nutrition.org/content/81/2/388.short

    http://ajcn.nutrition.org/content/81/1/16.short

    http://ajcn.nutrition.org/content/81/1/16.short

  192. I do not create many responses, however after browsing a few of the comments here
    Should Women Fast? | Mark’s Daily Apple. I do have a couple of questions for you if it’s okay.
    Could it be simply me or do a few of the comments look like they
    are left by brain dead individuals? 😛 And, if you are posting on other places, I’d like to keep up with anything new you have to post. Would you make a list of all of all your social community sites like your twitter feed, Facebook page or linkedin profile?

  193. I am a 28 year old female and I’ve been on IF for almost a month now. I have adopted a 16/8hr schedule, according to Leangains. Sometimes I push it to 18/6 if I am very busy, but that’s really uncomfortable at the end of the fast. I make sure I eat exactly as much as I burn. I have not tried fasted training yet.
    As far as I am concerned it has benefits and some drawbacks.

    Benefits:
    1. I am MUCH thinner and look much better
    2. Belly doesn’t bloat anymore, no matter how much I eat in one sitting
    3. My mind is much more clear, I can think better while fasting
    4. Greater output during training
    5. Energy levels don’t drop at all and my blood sugar seems to be much more stable
    6. I’ve dealt with random daily nausea for years, but that has completely vanished
    7. No more cravings for terrible food
    8. The happiness I experience when I have to eat large amounts of food really rejuvenates me psychologically. I have always hated the tiny meals of the ‘grazing’ method
    9. Food tastes INCREDIBLE
    10. So much free time during the fast, I get more things done, more quickly

    Drawbacks:
    1. I still wake up hungry
    2. My BM’s have become incredibly erratic, sometimes I don’t go for days, they are smaller and sometimes come with abdominal cramps. But, no bloating.
    3. If I have a slow day I am constantly thinking about food
    4. There are days where I sleep less, on other days I sleep more

    Looking at this I seem to experience more benefits. However, waking up hungry really bums me out. Like, seriously, that’s super annoying. I haven’t done this long enough to find out if IF affects my cycle. I am very curious about that!

    I hope my info helps 🙂

    1. FWIK, waking up hungry is usually low blood sugar. I try to have protein before bed and NO sugar (I rarely eat sugar or sweets anymore anyway), NO high-glycemic foods.

  194. I have PCOS and have been thinking about doing some water fasting, about 5 days. I don’t want to mess up my hormones any further, but on the other hand they’re already messed up. I’m not sure how to handle the situation.

  195. I’m a 37 yo female, martial artist, no medical conditions. Overall, lean and fit but I do still have a few extra baby pounds hanging on for dear life. With 2 young children, active lifestyle and ultra-busy schedule I think IF hasn’t worked for me because of additional stressors. My husband uses IF to great affect and does it twice per week. Usually he fasts on a regular day, but will fast on a different day if schedule/situation dictate.

    My experience, on the other hand, is completely different than his. I am a miserable wreck on IF. I am painfully hungry, have a bad attitude, low energy, wakefulness at night, painful morning and noticeable lack of strength. Although I had an initial weight loss with IF, it quickly rebounded and with a vengeance. I actually felt like my body’s response to short term IF (1 day and 2 day fasts were tried) was to add fat. I’ve had much better results by eating 5 small meals per day, “juice fasting” 1-3 of those meals every day and focusing on extra water intake. I choose a high-quality vegetable/fruit juice that packs in the vitamins on a small caloric load (usually 100-150 calories). Occasionally, I will juice fast nearly all day when my hunger is low but I never make it any longer than 16 hours without eating.

  196. Adding my experience for anyone still reading 🙂 (I’ve read many of your comments and appreciated them all!)

    I am a 31 year old female, 5’5, about 140 lbs, active via Crossfit (2x week) and biking to work. I am not a Primal eater, but rather follow the WAPF/Traditional Foods diet. I was on the pill for about 10 years (ugh) and went off one year ago. Menstrual cycle was very slow to come back, but started to after about 6 months. However, I decided to try the 5:2 diet seven weeks ago, just when my cycles were starting to get normal… and have not had a period since then (should have had 2 by now). My concern about this led me here, and I’m now feeling like IF certainly is not worth it for me. While I did lose about 10 lbs (which certainly wasn’t easy or fun), I do not want to put my fertility and hormones at risk. More fats for me I guess 🙂

  197. Hi Mark,

    I’m actually trying out fasting right now. I fasted on yom kippur and it didn’t go so well towards the end, which made me want to work on that. I’m doing a fast from 7am-7pm (because thats the only thing that fits my scheduale 🙁 ) with a workout before I eat, 3 days in a row, since more holidays are coming up and this is all the time I’ve got. So far, I seem to get really hungry around 1 when I would have eaten lunch. After that I’m fine. I’m REALLY surprised at how capable I am at working out on an empty stomach!

    I really appreciate this review of this topic for women specifically. Thanks!

  198. I am a woman and I have been practicing IF for most of my life without labeling it. I have never been a big breakfast eater. I would begrudgingly eat what my Mom put in front of me before school (Elementary age), and quickly started skipping breakfast most days once I reached Junior High. It just felt more natural to me. I felt less sluggish and more alert in the early AM on no food. My body naturally wants to eat somewhere between 10:00 am and 12:30 pm. I continued this pattern of eating through my adulthood even while pregnant. It never caused an issue for me. I started working out in my early 30’s, and tried to adopt the 6 small meal thing because everything I read said to do so. I felt less focused/more tired and after a bit of time eating like that would become ravenous and binge eat. Obviously I put on weight even though I was working out. I decided breakfast/6 small meals didn’t work for me, so I went back to my normal eating patterns, dropped the excess weight and focused again on building muscle. I eat once my body tells me to eat, and I normally aspire to eat my last meal at 6:00 pm although I do not stress myself out about it. This is of course just me….however if you have never been a big breakfast eater I wouldn’t recommend forcing yourself to eat it, and IF may work for you.

  199. I did intermittent fasting (16/8) for a year, and then I started to have menstrual cycle changes. I’m 45, and lo and behold, I was going into menopause! Not that I want to get pregnant, but I don’t want to be menopausal right now either! So I stopped the IF, and in 2 months, I was back to normal. I’m thin anyway, so IF is not necessarily something I “need” to do, but I’m always looking for ways to optimize my health. I’ll definitely do it again in my mid-50s because it saved time not to have breakfast and I felt fine. So I like what you wrote up here because men and women are different, and that ought to be a consideration for IF. It’s not “one size fits all.” If you want to give it a try, go for it, but if you don’t like how your body responds to it, give it up.

  200. Hi Ladies,
    I am a long term IF lady, it came as normal to me, for me, it’s always been the evening dinner as I don’t sleep well at nights with food in my stomach (perhaps was a Buddhist monk in my past life).
    Now as long as I remember, since a kid of 10, I have been never like eating later than 5pm and a light meal for that. But 10 years ago, I became very committed to yoga, and in the evening, it is my pranayama and meditation practise, hence, my last meal has to be 6 hours beforehand, which means around 2pm, the meal must finish. From 2pm to 8am the next day, I have nothing but water or hot teas.
    I loved the emptiness in the body as it helps to access deep spiritual insights.
    I love the expansiveness of the mind not hindered by a full heavy stomach.
    I eat pretty well since in my early 30s, especially, the last 15years, no junk, again, I was a fitness trainer, then a yoga teacher. My weight been pretty much the same since I was 17, I weigh around 48- 50kg on 163cm frame.
    I have always been super active and healthy, meaning rarely get any flus or colds while others are down and out in winters or any health concerns.
    However, 4 years ago, I started having a bad case of heart palpitations out of the blue, and was diagnosed as having benign ventricular ectopic beat. It may be benign but it is a huge clam down on my very active lifestyle.
    My mojo is seriously downtrodden!
    In the last years I noted that it is a lot worse when I am hungry, or menstruating.
    I felt that IF could mean a woman may not get enough nutrients in, so I researched and came across your article, and am every pleased you have shared so much knowledge.
    We don’t always absorb all the great food that we eat…
    I came to the realisation that it is what we eat, how we eat, our state of mind whilst eating and also how the body uses and absorbs the food.
    I have started taking a little protein shake or an avocado around 5pm now, and it helps settling my anxiety which also increases when I am hungry,
    I love IF, but long term health consequence, for me, it’s 20 years IF on a regular basis, the last 10 years ago IF every day, could have contributed to my heart electrical functioning, plus my over zealous practise/training, given the amount of food I consumed, I was never a cardio girl, but weights and long walks.
    I am now 48years old, 49 in 2 months, no sign of menopause yet, hair still all shades of dark brown.
    If anyone has any offer of advice, I would be most grateful and thank you all in advance.
    Take care, ladies, remember you are AWESOME!
    Xxx

    1. Ahimsa, from the Yoga Sutra, reminds us to do no harm. This includes to ourselves. I hope you have reached a place of kindness toward yourself as you enter your 50s 🙂

  201. All if the catty remarks between the little girls and the sexist remarks back and fourth both by little boys and by little girls make you all look like your still mentally stuck in high school. What a bunch of grown idiots! Grow the F up!

    My metabolism is ultra fast, I cant gain weight to save my life. Intermittent fasting caused adrenal fatigue where I was fine before adding in intermittent fasting and until I read this article I couldn’t figure out what was wrong with me.

  202. I wonder if the majority of problems women are experiencing are from restricting calories and not the IF itself. I think a 24 hr fast could be problematic because, say, over the course of a week it could be difficult to maintain an adequate calorie level. However, i find it hard to believe that eating in a reduced window of 8-10hrs (10 hr being recommended for women) with adequate calorie intake would be detrimental.

    IMO, women have a tendency to slip into undereating tendencies and IF could definitely exacerbate or at least facilitate this. These anecdotal stories are great and I enjoy reading them, but until we have well controlled, condensed feeding window with ADEQUATE calories studies on women we can’t truly know the effects of IF.

  203. Hi Mark,

    I recently tried IF and i did the 36 hour one. I would say throughout the day i wasn’t even hungry. I think i only felt hungry twice. And it wasn’t the STARVING hungry either. But one thing i noticed – is that the morning of the 36th hour (7am) i felt exhausted. I could barely accomplish anything. Now i’m not sure if i maybe just didn’t get a good sleep, but as far as i’m concerned – i get a sleep like that every night. I kept up on plenty of water. Just wanted to let everyone know how i felt … and if that’s natural? This is my first attempt at IF.

    Thanks!

  204. I am a model,30yr old, 5’81/2″ and since I have some pressure in keeping a certain shape I thought perhaps IF would be a good way of keeping a steady weight whilst allowing for some late night “treats”. Oh boy was I wrong. I went from being 125pounds to 132 pounds in a couple of months, my metabolism seems to have slowed down and my periods went from being 6 days long to 1-2 days long. I have always been healthy,regular periods, I eat mostly paleo (although champagne,wine and occassional restaurant dessert is my weakness), I run, do power plate, yoga flow and pilates. I only eat full fat, and lots of it… It has always worked a treat. I always hovered around the 125 pound mark, give or take a couple of pounds. Then everyone raved about 5/2 so I thought to try it -I did IF a couple of times a week- I followed the book and did 36hr fasts. It worked for a little bit- I lost a couple of pounds and felt very energised, but then the trouble started. Insomnia, ravenous hunger on off days ( i never ever got hungry like that before), and shortened periods. Now, IF doesn’t make me lose weight anymore. Even if I do a 500calorie day, there is no weight loss AT ALL, and the next day , with normal calorific intake, I put on weight instead. The scales have been creeping up-eek! I understand I am still slim for my height and I am not saying I NEED to lose weight, but I do notice quite a bit of fat deposits around my mid section ( I always used to only put on weight around my hips), which makes me think something bad is happening. I am working on just going back to how I did things before – 2-3 meals a day to fullness, WHEN eating, fast for 14hrs overnight, exercise on empty stomach, eat 1 hr after exercise .Now I just want my old body/metabolism back. Do you think it can come back? HELP!

  205. Hi my name is Martine and I have been on IF for a little over a week now and I feel fine. I do not feel weak. My body adapted to the change. I did feel a bit scared to try it cause I have heard so many bad things can happen especially if you are a woman, but thankfully nothing happened to me. I feel great and all my friends noticed the changes. I look better cause I dropped 10lbs since I started. I am happy about that. I truly think I can make this become a lifestyle for me. I can stick to it three weeks on one week off. I exercised moderately like three times a day(yoga). I feel wonderful. At the beginning I did feel a bit nauseous though but it went away now. IF works for me.

  206. I know I’m late to the party on this thread, but I just had to add a bit of my experiences to it.
    I’m a woman. I’m 66. Post menopausal obviously. Two years out from chemo, radiation, and stem cell transplant therapy.
    Without realizing it I’ve been gradually shifting to something like paleo eating.
    I’ve lost 50 pounds in the past three years and wouldn’t mind dropping another 20.
    Now, to what I really want to say. The biggest mistake I ever made was to do week long fasts when I was in my twenties.
    Each time I regained more weight than I’d lost. It became harder and harder to lose weight.
    Then, around the time I entered menopause, I began gaining weight in spite of eating only a thousand calories a day and running. I also got severely depressed and lost a lot of hair.
    Blood work revealed that I had Hashimoto’s Syndrome, which is an auto-immune disease that is inheritated. My problems had nothing to do with diet.
    My point is that, just because something happens around the time of menopause, doesn’t mean it actually has anything to do with menopause. So I advise all women to get a complete check up if they are having problems.
    That said, I am using your books and site to shift even more to the paleo way of eating simply because it makes sense to me that our bodies are more in tune with a million years of development than they are to the past 10,000 years.
    Oh, and I’m also adding Mindful Eating and Breathing to my efforts, because it seems to me that paying more attention to what I’m eating, what I want to eat and when I begin to feel full is an important step as well. The breathing seems useful to slow me down and help me pay better attention to my body.

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  208. I am 5’5 and currently 120 lbs. I have been doing the I.F for 5 months now. I am 34 years old and a mother of 4, my youngest being 9 months old. I started off at 139 lbs. With each child I gained about 10 lbs and at my biggest I was 150lbs. I have had no problems with I.F. it is the easiest way to lose weight for myself and for my husband. I never have been able to break 127lbs.

  209. I am a 45 year old female nutritionist, nurse and personal trainer. I counsel people on their diets and train them as well. I have been getting many asking me about a fasting protocol for weight loss and decided to try it myself. I do not need to lose weight per se but thought I’d see what effects it may have on my body. They were all positive. I did drop my body fat percentage by 2 points, noted an increase in alertness, and was able to cut out my morning coffee. At 45 I’m not menopausal nor perimenopausal, I think my paleo style of eating and exercise has kept me physically younger than most. I think the take-home here is everyone’s biology is different whether you’re comparing women to men or women to other women. Would I prescribe it for my type II diabetics? No, like Mark said one must be a fat burner first. But for most of my other clients and patients, I would if they already had their diet under control and needed the extra boost to reach their goals.

  210. I am a 42 year old pre-menopausal woman who is on depo (so no cycles anyway). I have been doing daily 16/8 14/10 cycles (listening to body hunger) and I choose to eat upon waking and stop eating between 4-5pm.

    I am technically “overweight” by the scale but at 5’8″ and 205 lbs I’m a size 10/12. I also lift heavy but have not been to the gym in eight weeks.

    Frankly, the HGH gains brought me to IF. I wanted the youth, muscle mass, and cognition benefits and didn’t much care about the possible masculinization. I DO worry a bit about the glucose tolerance, but as a low carber (generally) I suspect it has less effect, since my body burns ketones.

    Thus far in 3 weeks I’ve dropped a ton of weight. 16 pounds to be exact. I sleep just fine. The big problem for me is getting in enough fat and protein in the 8-10 hour window. My macros right now are 70% fat, 25% protein, 5% non-grain non sugar carbs.

    I didn’t want to lose weight, so this is an interesting side effect. I used to be obese, and wasn’t an overeater. I knew my problem was insulin, hormones, and genetics which is why I turned to ketones and lifting. So I wonder if MY experience with IF is because of those differences in hormones.

  211. Dear Mark,

    thank you for yet another great post. I am a 37 year old woman who is brestfeeding my youngest daughter (1,5 years old) and who has followd the Dietdoctor version of low carb for a bit more than four years. Through this I have lost about 15 kg:s of excess weight and gained many health benefits such as less sleep needed, healthier skin etc. During this process I found that I no longer feel hungry in the mornings. This made me want to test 16/8 so make it easier for me not to eat when I am not hungry. I have tried this (not too strictly) for about a month now and it seems i naturally fall into a rythm of 14/10 or sometimes 15/9. 16/8 would require some struggle. The biggest benefit is the feeling I have in the mornings. I enjoy eating when I am hungry. It seems I need a night fast of at least 12 hours in this respect.

  212. Somewhat off topic..

    …”Same goes for ultra-long fasts, like a 36 (or even 24) hour marathon. Most of all, though, I’d simply suggest that women interested in fasting be cautious, be self-aware, and only do so if it comes naturally. It shouldn’t be a struggle (for anyone, really).”…

    This line made me think of how when a woman is giving birth in most hospitals, food is denied her. If a woman is giving birth and wants to eat, let her eat! On the flip side, some women don’t get hungry during a birth, which is fine if she is allowed to listen to her body.

    My most recent birth (I hadn’t even heard of PB yet) I had steak, potatoes, and greens for dinner. The energy I got from eating food, helped me go on. Out of the three births (thus far) this one was my most Primal.

    After all, birthing is a marathon. (The soreness afterwards told me it was a major workout lol.) I need fuel to keep going!

    We now may resume our original topic of IF. (lol)

    KR

  213. Has there been any effort, in any studies, to determine whether an individual’s long-term diet-and-exercise regime (particularly while growing up) influences their later response to IF, and whether those experiences themselves display any gender bias?

  214. HI

    I want to respectfully submit my experience with fasting. I am a 48 year old female about to embark on another fast and very excited to do so. I did my first fast about 15 years ago. At the time, I was exhausted, both physically and psychologically from an overload of work and personal stressors. My hair was thin and frizzy, my skin pale and for my age, I definitely looked “older”. I had a puffy abdomen and was tired all the time. I frequently had tension headaches. I was drinking a lot of coffee and alcohol. My fast at that time wasn’t planned, it just seemed I fell naturally into a pattern of eating very little. I noticed after a few days of eating very little, I felt slightly better. I began to observe the physical effects more closely. Days past and I continued to eat little but some soup, juices and maybe herbal tea. The portions were tiny. I was far from hungry. It was a bit scary, not wanting to eat and not even craving anything. I didn’t want booze, I didn’t want sweets. The longer I went, the easier and easier it got. Then I started noticing changes in my hair. You would think without all those nutrients my hair would get even worse, right? My hair dresser was always pushing vitamins on me and telling me to crank up the protein to make my hair better. Well, it was coming in lustrous and full. I had never seen hair like this before. Me, of the frizzy “hair problem” hair was suddenly getting compliments on my hair. “Your hair is gorgeous!” “I have never seen such beautiful hair before!” It was bizarre and fantastic at the same time. Also, I didn’t have to blow dry it or curl it anymore. I would air dry it and would fall into fantastic natural waves. That’s when I knew I was onto something incredible here. My weight dropped gradually to a about 119 pounds and that’s where I stayed for a long. I felt fantasic and full of energy. My mood was great. My skin glowing. This is all true, I have no books or products to sell and this isn’t even my real name. I don’t want anyone to contact me, I’m just telling you what I did. Then I slowly went back to old ways. I was back to drinking, boozing and eating junk by the next year. I don’t even know why, why I would do such a thing when I felt so fantastic, but peer pressure kicked in. Soon I had gained weight, was feeling puffy and low energy again. I was surrounded by people who didn’t support a healhty lifestyle and realized I had to get rid of the bad influences. It is not easy to maintain regular fasts when people don’t believe in it or think you’re crazy. However my change in appearance was enough for me to see the truth…that fasting has amazing healing and health benefits. Maybe some women don’t take well to it, you have to know your own body. Me? I respond very well to fasting, it lightens my mood and body and I have physical proof of its benefits every time.

    1. Let me just add to this, I realize you are talking about IF and not long term fasting but I belive in both forms and practice them. Obviously, long term should be far and few between and IF can be done regularly. Let me further add that at age 48 I am a size 4/6, have absolutely no health problems (minus the occasional tension headache), take no medications, take no supplements and eat a primarily plant based diet with meat, fish, eggs or poultry 2 times weekly.

  215. I am a 45 yr old female and I fast once or twice a year (for 5 years) and I guess I can go about 12 – 16 days and then I am done. Fasting is wonderful. I move into ketosis and have excellent energy, (I have a greater spiritual connection to Jesus, and God answers prayer in amazing ways), I drop fat, and inflammation disappears. What’s not good?

  216. I am a 57 who has done some version of IF since I was perimenopausal at age 50. It actually had a positive affect on menstruation because it shortened the length of menses. I would menstruate for at least a week. IF cut that down to 3 – 5 days. I think that it is great and wish I had done this since birth.

    Let’s journey back to when I first began Atkins in my 40s. Once I began Atkins, I had noticed a sudden cessation to migraine headaches even though I continued experiencing the auras. Once I added IF to my regimen, The auras also stopped.

    Now, I eat one large nutrient dense low carb high fat meal a day. I don’t workout but I do pack on physical activity by walking, sprinting, burpees. And when I do these activities, it is when I am fasted. HOWEVER, I do use MCT oil during my fasting window. It is my goal to run a 5K race while fasted, when I turn 60.

    When I began fasting, I did it by eat breakfast progressively later each week. For example for 2 weeks I ate a 7:00 AM instead of 6:00. Then I began eating breakfast at 9:00 then eventually 11:00 then 12:00 noon. Eventually I made it to 2. Then I would eat whatever I wanted within a 4 hour window. Now that being said, I didn’t eat much during that window; just one large meal and a small one at the end of the window. My goal was not to reduce calories but to allow my gut to complete its work and rest in between meals. Fasting enhances the human growth hormone which also enhances testosterone as it also affects insulin so it is to not surprise that it will affect estrogen.

  217. One important note:

    “Perimenopausal” does not mean what you think it means (mentioned in the alternate day fasting reference above). Perimenopause is a period right before a woman enters menopause, not “childbearing age.” That study in fact *included* women who weren’t in menopause and women who were. It *excluded* women who were about to enter menopause.

    This is a very important clarification!

  218. I’ve been practicing daily intermittent fasting for 6 months on a 19:5 schedule. I’ve lost 36 lbs and feel amazing. This is the only intervention that has enabled me to take control of my appetite. Saying that IF is detrimental for all women, is like saying there’s a diet that’s perfect for everyone. Regardless of statistics and rat studies, at the end of the day, everyone has to be their own “study of one.” I hope other women won’t be discouraged to try it and will find out for themselves.

  219. Would love to hear someone knowledgeable’s input on this.

    I am:
    a 26 year old female
    5’9″ and in overall good health
    someone with an affinity for putting on muscle

    In the last year I adopted a paleo lifestyle and IF. I dropped 20 pounds (went from 170-150lbs). I didn’t know I could even lose this much, but I am in the best shape of my life, or so it would seem. I have a lot of muscle definition, and can also lift a lot of weight. I work out 4-5x/week for 30-60min at a time.

    However, since I lost the weight, I also stopped having a period. In addition, I am having trouble falling asleep and staying asleep at night. Other than that, I don’t have any problems, but these seem to be warning signs to me.

    I don’t want to gain weight back– I like the way I look and feel– but I also want to protect my fertility and bone density.

    Any thoughts on the matter would be appreciated!

    Thanks 🙂

    1. Women need some fat for hormonal purposes and to have a period. I’m not sure if we need that fat on our bodies or just need to be ingesting enough good quality fats like organic coconut oil, grass-fed lard and butter. (I’m post menopausal so can’t experiment with this.)

      You may just need to add some more fat to your diet. If your body is good at digesting fat, this won’t make you fat.

      Another idea is to look for a functional medicine practitioner and have some saliva and urine testing done to start. You can also do it on your own:
      http://functionaldiagnosticnutrition.com

  220. The research you cited is statistically horrible.
    Sample sizes of about 10 women
    Cmon man…

  221. In terms of the “no other excuse” for not losing weight – I have struggled with my weight and debilitating fatigue since my early 20s until I was finally diagnosed as hypothyroid in my early 40s. I also discovered quite late in life that I was wheat intolerant. That really motivated me to eliminate wheat, though I’m not quite ready to go full primal. Further, all the caloric intake levels I was told were dead wrong because they were far too high. Maybe others of you don’t have to, but I absolutely have to count calories because I am not currently able to exercise thanks to a slew of injuries. Even walking hurts. So I’m using IM (skipping breakfast) as a way of stimulating some level of fat burning that I wouldn’t otherwise be getting.

    Women do have legit considerations with hormones causing changes to digestive processes. High levels of estrogen and progesterone can slow everything down. And menopause may cause some metabolic changes. Just my 2 cents.

  222. I read somewhere that study did not take into account that a lot of perimenopausal women are on birth control. That women not on birth contro had no problem with fasting and benefited just as much as men. Amyone else hear this? I have no problem fasting 16/8 5 times a week. I work nights and have my last meal at 4 on work nights nd am lax on nights off but never eat after 8. I still ovulate and get regular periods. It seems the same things that promote egg quality also could ironically stop ovulation…such as exercising and fasting. I think it is a fine line you have to do just enough but not too much…a bit of a quandary for us womem

  223. I realize this is an older post, but I’ve been trying to research intermittent fasting for women and still not much there…so I’d like to put forth my experience. I’m in my early 60’s and started IF a couple years ago. It’s been great! I never had a weight problem til my mid-40’s when I did a career change that was more desk oriented. Gained 40+ lbs. Lost it on WW online and then gained back 10-15 lb over the course of 15+ years. I wasn’t into doing portion control, and had heard of IF. I started with the 5:2 for several months and after losing my weight, moved on to the 8 hr eating window. I don’t fast on weekends as it’s a family time and we enjoy our meals together.
    As I think on it, I believe I was doing IF all my early years, tho’ with a 12 hr eating window most days. I had a job where I had to be at work at 6 a.m. , so breakfast wasn’t generally eating. And often we didn’t always get lunch… (i worked in a hospital medical lab).
    I had a physical a few weeks back and my labs were all great… My BP normal and I’m on no meds. My HDL is >100, so that does put my total cholesterol up there, but dr said that was great as my ratios were awesome.
    I try and eat 4-6 fruits/veggies day and eat mostly whole, minimally processed foods along with exercising and minimal weight lifting.
    All in all I feel the IF has helped control my mindless eating (which isn’t good even with a healthy diet) and I appreciate my food more.
    I’ve probably rambled on enough, but thanks for letting me do so 🙂

    1. Thank you for that. I’m 59 and post menopausal as well. I’ve been doing IF in 8-10 hour windows for the past few months and no ill-effects. The best thing I’d ever done for my night-time silent reflux is not eat 4 hours before bed — that’s what accidentally got me started on IF.

      Until there’s a substantial study, I’m ignoring the warnings about women and IF. There are too many variables unaccounted for to rely on them.

      Terrible sentence. Need more coffee…

      Actually, that’s my question and why I’m searching IF today: I thought fats during the fast (butter and/or coconut oil in my coffee) do not break the fast. But I can’t find any info on that.

      Leangains Martin says sugar-free sweetener and a dash of milk won’t break it (and of course a dose of BCAAs if you are fasting-training but I’m not).

      What’s the scoop with fats during fasting? Does it break the fast or not? Thank you!

  224. No conclusions should be drawn from those studies either pro or con with regard to IF for women. None of the studies are big enough or long enough to measure anything reliably.

  225. Hello all, I am new to this blog but I wanted to add something that has happened to me whilst doing the IF thingymagig!! I am 52 and I suppose i am post menopausal seeing as I havent had a period for a year or just over……until today!!! Well…..I was very surprised and remember reading something about hormonal imbalances whilst doing the IF…. Its not full on but I have had to go buy stuff that I havent had to for a year!
    As for the IF….I LOVE IT…i feel better already and it has only been nearly two weeks..I feel more awake and still sleep at night…..my body has stoped aching so much and mood wise I feel so much more balanced….
    Please dont tell me I have to stop it….I tried fasting on Mondays and Thursdays before but found myself getting very moody those days and not losing any weight at all…this way I eat after 11 and stop at 7 …easy and if I want chocolate i eat it….but I find I dont want to binge at all..,unlike when I was doing the two fasting days…..so thios has worked for me apart from the period thingy!! I will keep an eye on it and hope that it balances out again and yes i will visit the docs to check to make sure everything else is ok..I just wanted to say IT WORKS FOR ME……hopefully I dont have to stop because of this period thing……really dont want them back…I mean it is the only thing about menopause that is a great thing for me,….

  226. I am a guy who stubbornly resisted fasting for 5 1/5 years because I was getting pretty good results. After starting mostly eating in a mostly 11 am to 6:30 pm window, I am getting fabulous results. Fat melting off and twice as much energy. I think IF is essential for guys (after becoming fat adapted, which is also essential.) That’s how we hunter Groks evolved.

    But it is wonderful to see some thought about how women differ. Too little of that in medical research.

  227. For what it’s worth, I am a Muslim, and I never found the fasting of Ramadan to be detrimental to my health in any way. Keep in mind that I elected not to fast when I knew that I was pregnant or breastfeeding before introducing solids. In fact, I have found that it actually brings ON my period if I was previously in a state of post-first-year breastfeeding amenorrhea. Both times that I have fasted Ramadan after having been breastfeeding for a year with absolutely no menstruation, my period came back within a week. As a Muslim, I believe that the commands of God are inherently good for me, and the Islamic rituals have been confirmed to be very health-giving practices over and over again. For this reason, I would also add that I wouldn’t recommend fasting DURING your period because it is forbidden in Islam, and I trust that it is so for a good reason. One possible side effect could be that it would disrupt your cycle. That may be where women are running into problems with IF, either fasting for too long or trying to do it while menstruating. Also, breaking the fast with dates may be helpful as well. I believe I’ve read before that dates contain some bioidentical hormones that make them helpful during childbirth.

  228. Hello there!

    I’m a 23 year old woman from Hamburg, Germany. I had some good and some bad experiences with IF. First I went paleo and in order to lean out I started 16/8 IF. That really helped.
    But I went further to almost 24 hours of fasting and allowing myself only a 2 hour window of eating, mostly high fat low carb. At first I didn’t experience anything bad. But out of a sudden I couldn’t sleep during the nights, felt exhausted during the days and developed a pretty bad temper (I felt like anyone would criticize me-even by saying “hi”).
    It was a very hard time and finally I was diagnosed with adrenal fatigue. I can’t tell if that comes from my fasting or from the very low carb intake but I sure won’t try IF for more than 16 hours again.
    Right now I am on a healing process but as always that takes much longer than ruining your body or hormones. 😉
    Thanks a lot for your post and keep up the good work! 🙂
    Henrike

  229. What about IF for pistmenauposal women?
    I am 71 yr. Old, and it seemed to work for me last year

    I have glucose intolerance, but am not diabetic.

    Thank you,

    Louise La salle

  230. This is awesome. I am so glad to get this advice. I did IF 19/5 for three months last year and lost more than 20#, but then, I had a less than healthy winter and by summer was up that weight exactly. I am 50, and struggling with the end of perimenopause, and have off and on over the last year re-tried the 19/5 or even longer fasts without the same outcomes as a year ago. Think I will give it a rest until I get enough rest and “health” back for it to have its initial effect. That 20# loss felt so good and this 20# gain feels terrible.

  231. I am a 41 year old woman. I tried 5:2 (one with 600 calorie restriction) two years ago with very good results. I was not overweight then so did not have an ambitious weight loss plan, just wanted to lose few extra pounds. I lost approx. 8 pounds in 4 months following 5:2. I stopped IF after I reached my weight loss goal but mainly because my work life became extremely stressful around that time and I struggled to count 500 calories at dinner and plan meals accordingly (I never managed to count successfully). I have started IF again two weeks ago and this time doing 24 hour fasting (7 pm one day to 7 pm next day). I do allow myself a cup of tea at breakfast time. I drink plenty of water. On fasting days I go for brisk walks and my hunger goes away almost immediately and I feel very energetic. in fact one fasting day I did not go for a walk and I felt more hungry. I think a little exercise help me on fasting days. My hunger usually comes back around 3/4 pm but goes away again. I do 24 hour fasting twice a week and rest 5 days I eat normally. I should mention I don’t eat breakfast anyway and most of my adult life I have skipped breakfast. So 24 hour fasting days only means I skip one meal (lunch). My BMI is healthy but since I had to stop regular cycling I put on 6- 7 pounds in last 6 months. I am planning to shed this and intend to carry on with the 24 hour fasting. I may do only one 24 hour fasting per week. I generally find it very easy to follow. I don’t count calories. I do drink alcohol (5/6 units per week) but since starting IF I am less keen on my usual glass of wine. I remember wine I had no issues with period, stress, anger, sleeplessness. In fact I have the opposite effect. I feel brilliant. I lost 2 pounds already.

  232. I have quite some experience of fasting. 10 years ago when I was around 20 it worked really good for me to loose weight to do IF. Over the years it’s very clear though that it has benefitted me less and less and possibly even contributed to some seroious health issues (problems with intestines and metabolism etc).

  233. I am a 44 year old woman. I have lost 105 pounds over the last 23 months via Keto. I am fat adapted, but I am also Type 2 Diabetic and been off meds since May 2014. The last 2-3 months, my fasting blood sugar somehow decided to start rising. Where I was in the 70-90 range for over a year, a few months ago I started getting readings mostly in the 90’s and sometimes over 100 with the highest being 118.

    This was stressing me out because I was/.am still Keto and thought I might be broken or something! I tried IF in the hopes that it would help my blood sugar. What I found was that if I did a 22-24 hour fast my blood sugar was 70-85 and my Ketones were over 2.0 but with the 16/8 window there was NO improvement.

    So now I have decided that IF does not work for me. I think I will do a 24 hour fast once a week, but otherwise I am going to remain with my routine of eating when hungry. Also, I did finally figure out the secret to my morning blood sugar (at least it seems to be the secret so far) and that is to have a fatty drink before bed (either a Keto hot chocolate or broth./butter drink) and miraculously my fasting blood sugar has returned to the 80’s!

    This was a great article and validated some of my recent thoughts and it really helped me!!

  234. I had a biology teacher strongly suggest fasting roughly 20 years ago. Very fit, healthy man. Never once suggested it was different for men than for women. I have done it throughout my life (though I never studied it, nor did it have a catchy name like “IF”). It’s always been how I’ve managed my weight. The best I ever felt, and the best shape I was ever in was in my late 40s… I was in college full time, ran (jogged) a couple miles 5x a week at 5am before leaving for school, did 60 pushups/day, ate one healthy meal a day in the afternoon, and never after 6 or 7 pm. I realized later I was pre-menopausal, but had no idea at the time. I felt great, had great energy. (Except for those nights when I woke up in a sweat, LOL….) An “A” student. …. Another time, I did a 3-day juice fast prior to going gluten free for 6 months. The worst part initially is hunger (and catching flack from people who want to forever shove food in your face), but it fades over time, and then you don’t think about it. I rarely eat breakfast, and always feel better, lighter, more alert when I fast. When I’m not fasting (which is most of the time 😉 ), I follow a “pescatarian” diet, limiting dairy products as much as possible. I’m 105, 5′ 2″, and in perfect health aside from being on the low side of normal with regards to vitamin D. (Mostly because I don’t get out in the sun enough.) My 2 cents. I’m 50, and people think I’m 30-something (but I’m pretty sure that’s because of genes, and staying out of the sun.) My 2 cents.

  235. So how often do you have to eat then to make your body not think it’s fasting….?

  236. Hi, Mark. Just read your post.

    Well, first of all, I think it’s not a good idea to use findings from animal studies for human cases.

    Also, I think that intermittent fasting can be good and bad for women. It depends on body fat proportions and how long you fast. Here are two studies –

    The 1st study – Eight lean women with a BMI of 20 or less and a body fat % of 20 or less, were asked to fast for 72 hours during the midfollicular phase of their menstrual cycle. They lost almost 5 pounds and saw increased levels of cortisol, and delayed follicular development. (Alvero at el. Effects of fasting on neuroendocrine function and follicle development in lean women.J Clin Endocrinol Metab. 1998)

    The 2nd study – 12 women with 25% body fat were also asked to fast for 72 hours during the same phase as the lean women. Researchers found that follicle development was similar in all cycles and was followed by ovulation in all
    women. (Olson BR et al. 1995 Short-term fasting affects luteinizing hormone secretory dynamics but not reproductive function in normal-weight sedentary women. J Clin Endocrinol Metab. )

    So it look likes that the less body fat a woman has the shorter her fast must be. We have a lot of women who fast for 24 hours once or twice a week and feel fine. We published some women stories on this page – http://www.eatstopeat.org/intermittent-fasting-for-women-what-results-you-can-expect/

  237. I had lived with digestive problems for over ten years when I decided to try fasting as a way of letting my gut heal on its own. I had seen countless doctors (k not countless maybe, but many over the years), tried all sorts of diets and pills that were supposed to help, more fibre… You name it, I’ve tried it.

    So. Many times I had come across articles on how fasting would give your gut time to heal since it didn’t have to process any food, but I always thought it seemed too extreme. Plus, I was terrefied of going hungry. Don’t like being hungry but also – low bloodsugar turns me into a fire breething dragon. I was worried for my loved ones. But finally I had to do something and decided to try.

    I followed advice, and crossed over to a vegitarian diet two weeks prior to fasting. During the fast I drank vegetable juice, green tea, vegetable stock and lots of water. No caffeine, no nicotine. Did it for a whole week and imagine my surprise when I felt hungry only once, and that was on the first day. By day seven I was feeling energetic, happy, no mood swings and all of a sudden I was waking up in the morning with a smile on my face. Now that has NEVER happened before.

    So, like Mark said. Try it for yourself. Only you and your body can tell if it’s going to work for you. Oh. My digestive problems got better by at least 80 percent, so it was worth it. So worth it.

    I was 33 at the time.

  238. I am a 32 year old female and did this fast for 7 months. I lost 70 pounds (270 to 200) and had zero negative affects as far as i could tell. I had a partial hysterectomy when I was 29, i wonder if that has anything to do with it. Interesting. Thanks.

  239. Hello! I started the ketogenic diet for medical reasons (migraines) and have also been doing IF’s for the same reason. However, I have only gained weight (!) even controlling my macros and eating only WHEN as you say. I am not obese, in fact, I am thin and have had no trouble keeping my body weight throughout my life. I am 47 now. I’m completely convinced about this diet and decided even to start helping others to change their life as I did (I am completely free of my migraines) and started attending your Primal Health Coach program. However, I’m not happy with my weight gain and even with all my efforts (controlling macros, IF, and controlling calories) my weight AND measurements are not improving as I expected. Do you think I must be in starvation mode? What can I do about it?

  240. I’m 45 and I’m attempting to IF from 8pm to 12 or 1pm. I’ve been doing it for the last two weeks but I can’t seem to adjust. My blood sugar gets low and I feel so hungry even when I do bulletproof coffee and consume lots of fat in the morning. I just can’t seem to trick my body: it wants carbs and it wants my blood sugar raised to a comfortable level. I’m not eating a high carbohydrate diet but if I don’t eat enough carbs in the evening I keep getting hungry signal from my stomach until I give it enough carbs and then finally I feel OK and I can relax. Combining the carbs with plenty of fat protein and vegetables helps it to last longer. Still I wake up hungry but since I’m not physically active in the morning I can force myself to wait until mid day to eat. Is this normal? I’m not supposed to feel hungry eating all the fat but until my blood sugar gets raised to a normal level I continuously feel hungry and Uncomfortable until I do. I feel guilty because I’m supposed to limit carbs but I can’t fool my body. Will this feeling of hunger go away after a few weeks? I can feel when I have low blood sugar.

  241. I’m a 42 yo female, no signs of menopause. I was doing 16/8 fasting for a couple months. I have recently noticed a huge dramatic loss in hair. I feel like about half of it is gone and have had clumps come out in the shower. I’m stopping IF but find it hard to eat in the morning as I am aftesud to gain weight and am never hungry. Really worried about my hair loss. I had beautiful full hair and now it is half gone.

  242. I’m a 50 year old woman who has “slipped” off primal in the last year or so, gained 10 kg and I suspect IF was a significant factor in this.

    I went primal in 2011 at 45. As an ex chef I love food and have always believed fresh and whole is best, have eaten very clean, eschewed most processed food, always used butter and olive oil to cook etc so the main primal shift for me was ditching the grains and sugar. Primal worked really well for me and I felt better than ever.

    Over the course of the ensuing 5 years I moved from pre-menopausal through peri and almost into post menopausal so have seen the related transitional changes within my body. For the first couple of years doing primal the odd IF worked relatively well for me as long as I kept it short – say 12/12 with perhaps a small cup of chicken broth if I really needed it. Round about 48 as peri kicked in, even eating primally I was struggling with sleeping patterns, weight gain, lack of energy so I thought I would try a bit more regular IF – once a week for about 6 months. My energy levels improved, the extra kilos didn’t exactly melt off but they did go. At the end of that 6 months however once I stopped IF, it was as though my body had shifted into starvation mode. My capacity to control food cravings went west and I started eating like I’d never see food again – still good primal food but the satiety factor had gone. I struggled with it for about 3-4 months then thinking IF had worked last time, I tried again (my mistake). I did IF for a month and found I just couldn’t do it – on the IF days, my brain shut down, I felt like I was walking through quicksand and I became almost incoherent so very quickly stopped. The backlash this time was much worse and has lasted much longer – almost a year.

    To round out the picture, during the course of the 5 years, my exercise levels did not change and while I have been under quite a bit of stress for most of that time, in the last two I recognized this and have doing more mediation and expanding my yoga practice to help.

    Everyone is different and I’m no science buff but I suspect that for some peri and menopausal women, the restriction of food creates a serious stress reaction in the body which in addition to hormonal change stress means IF is not a good option at all.

  243. I’m glad people are still posting to this as I just discovered it today. Read all posts and found nobody like me: doing *medically supervised* HCG diet 4th round (low calorie diet of 500 cal per day) for about 6 months. Also 46 yo female, 2 kids, post menopausal due to ovaries removed. Switched to HCG 2.0 (keto) and lost all hunger, ended up doing IF even while being on extreme low cal diet. No problems yet and I do feel like I have better focus. (Several HCGers do some IF like HCGChica, post HCG, though!) Few things I learned others have mentioned: hunger really only went away when carbs were less than 30g per day for me, dizziness happens often when you need Potassium (track it and supplement carefully because bad if too little or too much), and yes, for some reason a few HCGers (but not all) seem to get messed up metabolisms which might be similar to IF issues. In that case people try the FAST metabolism diet which seems opposite of fasting but those people seemed to be helped. Because of my low cal dieting I found this site to figure out my next steps to help with maintenance to not regain weight. I am worried about metabolism and may do 2:5 or fast metabolism diet, still undecided. Oh and hair loss happens with low cal/carb. I have tried mixing aloe vera with MSM and rubbed in as a topical solution on skin, not hair, and it has helped somewhat. Hopefully my post helps someone.

    Finally I wish there were more posts/studies on fasting for cancer prevention vs general health. Does IF of less than 24 hours really help for that or you need to do 24 hours plus? Anyone point to more studies?

  244. I’m 60 and post-menopausal. I’ve been low-carb Paleo for a couple of years, but have just started doing IF a few months ago and love it (18-6 seems the best fit for me). Like someone else mentioned, I wasn’t too impressed with Stephanie’s article because it was too generalized. I find the IF has nothing but positive effects for me and I’m someone who had to have CBT for insomnia and use every sleep hack there is, so I would never do anything to jeopardize that (it irritates the hell out of me when Dave says, “I don’t have time to sleep 8 hours a night.” Is that humble-brag supposed to impress people? Anyway, that said, I’m not sure how well things would have gone for me in the days of PMS for those 2 days before menses. It may well have been too stressful then, but I welcomed menopause and saw it as a positive stage in life despite the fact that it did make gaining weight all too easy. Fortunately, I learned about low-carb and Paleo…All the best to you, Mark and all who’ve commented. I really enjoy MDA.

  245. Hello everyone,

    I am 34 and pre-menopausal. I have actually incorporated IF into my lifestyle for several years and it has been a wonderful experience for me.
    I do think everyone’s body is different and I believe that based on our body type/genetic background/blood type, etc – we all have different needs. It’s important to listen to our bodies to see what works and what does not. For some… IF doesn’t work.

    I started out first low carb and then when I was diagnosed with celiac I had transitioned to paleo. I was paleo for about a year before I started IF. When I started IF my body was already used to utilizing fat as energy and so this was an easy transition for me, being more mind over body and understanding the process of the brain and habits.

    Because my body is used to utilizing fat as energy, I’ve been able to really learn how to listen to my body and what I truly need. With my hormones changing throughout the month to complete my cycle, I actually change my IF throughout each week. Meaning, there are differing weeks when I fast 10-14 hours, then do 16 hours, then 18 and up to 20-36 hour fasts depending on where I am in my cycle and my energy levels. As I stated before, I am very in tune with my body and honestly I feel like IF has helped me increase that awareness. I have not have any menstrual problems and fasting has actually helped with the pms symptoms I used to experience.

    I train on a fasted state but if I train with weights, I break my fast earlier and if I train with endurance, I go longer. Again, I listen to my body.
    I started this journey about 180 lbs and over the course of the last several years. I’ve maintained a weight of about 120 – 125 (water weight throughout the month) on a 5’6 frame.

    IF might not work for everybody, but IF works for me and it makes my life more enjoyable and so much easier!

  246. I really wanted fasting to work. I’m overweight and have difficulty dieting. IF seemed like it would be perfect for me. My experience this week was sleeplessness, super fast, heavy heartbeat at night. No weight loss I started with 16:8, but then changed to 14:10. I really want this to work. I must mention I have hypoglycemia.

  247. I’m a 45 yr-old woman, peri-menopausal and slim but could use some toning. I started IF (12pm-8pm feeding daily) a few weeks ago and felt great. Increased energy, more mental clarity, and decreased digestion issues. I workout in the morning Mon-FRI and have recently noticed a huge decrease in lean muscle mass – all my hard work to gain the muscle is literally evaporating before my eyes! I eat wll, have enough protein and sleep enough. What am I doing wrong? Help!

  248. I’ll just add my 2 cents.

    I am a woman in my 50s, 5′ 3″, BMR of 800, current BMI of 25, and have PCOS (thus I’m insulin resistant) and am in the midst of perimenopause (thus estrogen-dominant, with excess cortisol). Until perimenopause, my BMI was 16…effortlessly. I never needed to lose weight until I started gaining fat in my 40s with no lifestyle change nor overeating.

    Skip ahead, past the months of daily exercise marathons, starvation, etc.

    I’ve been doing IF (20/4) for a month, with no weight loss.

    I’ve been eating an extremely healthy, plant-based diet for over 10 years, with low GL for at least 5 years, and according to the Insulin Index for several months, now. I eat comparatively very little food and am rarely hungry (evidently, I don’t produce much ghrelin). I exercise daily (moderately, these days, after an endocrinologist’s advice), with weights every other day.

    No amount of exercise leads to weight loss, wheras strenuous exercise most decidedly does lead to weight gain.

    I feel perfectly fine on IF. It simply hasn’t helped me lose any weight, all the while requiring me to exercise daily, and limit my eating to healthy, small meals during a brief window, despite social obligations, etc.

    I was saddened to read another article about IF and perimenopause which essentially said the “selling” of IF is the fact most young people can maintain or even lose weight with IF without exercise or watching what they eat too closely, but that is decidedly not true for women in perimenopause. The author claimed that we must exercise, reduce calories, eat very healthy and, even then, might not lose weight with IF.

    That’s been my experience, so far.

    You can’t burn body fat while you have insulin in your bloodstream. That is partly why IF is supposed to be more effective for fat loss than simple caloric reduction. (Multiple daily meals mean insulin will always be present in the bloodstream, and PCOS women, in particular, will always, then, be storing any calories they eat, as fat, because we produce excess insulin.) There are other alleged benefits of IF, such as atophagy. It all requires a period of fasting with no intake of dietary protein. IF is said to be especially beneficial for women with PCOS.

    But, as I indicated, I have been exercising more, eating less, and fasting for 20 hours per day, for the past month, and am no better off than when I started. In fact, given that nothing else has worked either, and this was the most hopeful I’ve been in ages that I might finally get a handle on this perimenopausal weight gain, I’m actually worse off, because I’m psychologically devastated it’s not working, and have resigned myself to near-starvation as the only strategy that has ever allowed me to lose weight.

    So, I didn’t eat today, and will eat a bowl of greens and a multivitamin tomorrow, and every other day, I guess. Maybe then I can lose a pound or…dare to dream…two? (I need to lose 20-30lbs, though.)

    Perimenopause sucks balls.

  249. 50 year old women, no signs of menopause. I have beeb tried all the protocolls of iF since 2 years ago. Finally 5 weeks ago, I started alternate day fasting ( only water fasting 3 days of the week). So far 4 kg ( 8 lbs ) less. But i was worry after reading about possibles consecuences… Well i feel great except the sleep issues ( which I always had). But, for me, it is the best method to lose weight. I could not change it.

  250. the 5:2 diet works best for me, I combine it with the 14:10 fast as well. When I eat I eat LCHF, all my targets are met, but I have found great weight loss and toning results. the shorts I bought 3 weeks ago are already starting to sit more loosely. I don’t really feel very different on the days I fast, perhaps because I usually eat fat and my body has some reserved energy to run on. Years ago on a high carb, low fat diet I use to feel very sick if I did not eat, this meant that I took almost a year before attempting 5:2.

  251. 26yo female. 18-hour fasting sent my migraine frequency from 2-3 a month to six in one week, so I gave up on that on day 7. I tried a less structured version by just skipping one meal a day and gave up again after a week because I’d gained 6 pounds, didn’t have the energy to run at all, and spent every waking moment completely fixated on food. Calorie restriction just isn’t for me.

  252. Which begs another question, which probably has zero studies, and that is the benefits or dangers of IF on POST menopausal women, 50 and upwards! 😀

  253. Thank you for the informative article! I had some interesting experiences with fasting. A few years back I had adrenal failure and my immune system was so weak that I unfortunately got a rare form of shingles referred to as Ramsay Hunt Syndrome. Basically you get shingles “inside” your face (the sores associated with shingles were in the ear, in the eye and down my throat) and it leads to paralyses of the facial nerves. My hair fell out, my nails stopped growing for two years and it took three months before any movement in my face returned. The pain was unbearable. I had this horrible disease in 2004 on the right side of my face and
    again in 2011 on the left side. With shingles the symptoms never really goes away. When ever I have a drop in my immune system – even with a common cold – the pain in my facial nerves would return. Through help of informative articles like yours I started experimenting with different healthy habits to maintain a healthy immune system. I was very overweight and unfit. I started with an exercise routine and healthy eating program. But as soon as the weight loss was to fast my immune system would weaken and the pain would return. I was tired all the time, struggled to concentrate and even had challenges with my memory. I could drink no coffee or any other caffeine loaded drinks because of the adrenal failure so that sporadic energy boost was out of the question. I then started experimenting with fasting. And now, a few years down the road, I am almost three dress sizes smaller, I am gradu