Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
19 Jun

Dear Mark: Women and Intermittent Fasting

Many differences exist between the two sexes. We look different. We sound different. We dress differently from each other. We like different things. Different genres of movies cause men and women to cry (differently). And although society, media, and culture drive and/or inform many of our differences, some are inherent and physiologically-driven. For example, men and women have different biological equipment – both external and invisible to the naked eye – that change how we interact with and respond to our environments, our exercise, our sleep, and our eating habits. Nowhere are these gender differences more evident than in the realm of health and nutrition, and yet it seems that I’ve overlooked a big one: different sex responses to intermittent fasting.

Let’s take a look at a couple recent reader emails:

Hi Mark,

I’m a woman (28 years old) who followed your recent fasting series with great interest, gave it a shot, but had mixed results. Then I read this post, which mentioned your series and questioned the suitability of intermittent fasting for women. Is it true? Do we respond differently than men? What do you think of that post? Thanks!


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

Thanks for writing in with your questions.

First of all, I really, really liked Stefani’s post. I should say “posts,” actually, since Stefani Ruper (who wrote the post linked in the reader question) also just did a guest post on Free the Animal, in which she discussed the treatment of women’s issues in the community at large. While I don’t agree with everything she said, both were quite well done.

Even though her articles – for lack of a better phrase – “called me out” (in a completely non-confrontational way), I was actually quite happy to read them. Heck, I was happy to read them because of it. After all, I’ve always encourage people to be critical about what they think they know about nutrition and fitness, and to be skeptical about what they read on the Internet – my articles included. The beauty of MDA is that it isn’t one-sided. I get constant feedback from readers that send me down new paths of inquiry, and it’s through this kind of crowd-sourced effort that the Primal Blueprint message grows and becomes stronger than it already is.

I also appreciated Stefani’s articles because they do highlight a blindspot – not just in my own series of posts, but in nutritional science as a whole. In the push to eliminate the confounder known as inherent endocrine gender differences, they’ve forgotten that real life is a series of confounding variables all pushing, pulling, poking, and prodding at the results we get. They’ve forgotten that while their results may represent fodder for publishing and accolade accumulation and hypothesis confirmation (or rejection), real live humans in normal living situations are not placebo-controlled. That women are not the same as men and respond differently to stimuli and stressors isn’t a “confounder”; it’s a fact deserving of further study! Because what are we ultimately trying to do here – put together nice, neat, peer-review-ready trials, or help real people living real lives?

Since I’m trying to do the latter, I happily accept constructive criticism. So should we all.

So, what did Stefani’s research find?

Fasting has different endocrine effects on male and female rats.

In male rats:

No matter the duration or degree of nutritional stress, male rat 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.

In humans, the male-female fasting literature is quite scant, but Stefani also found considerable differences beween the sexes, when data was available:

  • One study, which I’ve cited before as evidence of a benefit to fasting, 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. Ouch.
  • 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. Favorable, albeit sex-specific results.
  • 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 of reproductive age.

I figured I’d look through my other recent fasting posts for data on female (preferably pre-menopausal) responses to fasting. Here’s what I found:

  • 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.
  • 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. Takeaway: fasted endurance training, then, may work better for women than fasted weight training.

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.

As I alluded to earlier, this is what I love about this open forum we call the Internet: the fact that if you leave something out, or overlook a key point, someone will call you out on it, most likely publicly. When that happens, you grow despite yourself. If not for Stefani’s posts, I may never have taken a closer look at the inherent differences in men’s and women’s metabolic responses to fasting. I certainly receive enough feedback from female readers for whom fasting has been helpful, so it’s good to see another side.

To sum things up – if such a thing can even be done – and answer the questions in the intro, 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 adornment, a choice, a potentially therapeutic strategy that each individual must test for him or herself. Although my recent series on fasting might have thrown some people off, I want to reiterate that I am not a huge IF guy. For myself, 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.

So who should and 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. The 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, 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). 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.

I’m not going to say that women should or shouldn’t fast. I’ll just echo Stefani’s advice “to look at options, to be honest about priorities, and to listen to one’s body with awareness and love.” Frankly, everyone should be doing that, but with regards to fasting, it looks like women should probably hew a little closer to her words.

Of course, if I had to make one minor quibble with the content of Stefani’s otherwise outstanding posts, it would be her source for the number of unique visitors Mark’s Daily Apple gets each month. Nowadays, we’re actually getting closer to 1.5 million monthly uniques, not 250-300,000… but who’s counting?

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.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. FYI: Robb Wolf’s Paleo Solution podcast episode 136 discusses estrogen and paleo.

    Paleo Bon Rurgundy wrote on June 19th, 2012
  2. 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.

    KM wrote on June 19th, 2012
    • 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?

      Jodis wrote on June 19th, 2012
      • Meow!

        Paleo Bon Rurgundy wrote on June 19th, 2012
        • Inappropriate and sexist

          Tracy wrote on June 19th, 2012
        • lol

          rabbit_trail wrote on June 19th, 2012
        • I love Ron!

          Andrea wrote on June 20th, 2012
        • A woman disagreeing with someone does not warrant a “meow”, you are actively part of the problem.

          Lauren wrote on February 8th, 2013
      • 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…

        Primal Toad wrote on June 19th, 2012
        • 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!

          Jodis wrote on June 19th, 2012
        • 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…

          Primal Toad wrote on June 20th, 2012
      • 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.

        ML wrote on June 19th, 2012
        • 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.

          Rachel wrote on June 19th, 2012
        • 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.

          Lena wrote on June 20th, 2012
        • “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.

          Chloe wrote on June 20th, 2012
        • 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.

          Oceanside Grokette wrote on June 20th, 2012
        • 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!

          Elenor wrote on June 21st, 2012
        • 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!

          Michelle wrote on July 3rd, 2012
        • 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.

          Amy wrote on June 1st, 2014
        • 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

          jh wrote on December 27th, 2014
        • 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.

          Older Woman wrote on August 22nd, 2016
      • Er…could said it with a less snotty tone…..sheesh!

        Stacy wrote on October 30th, 2013
        • And I was referring to Jodi’s comment to KM.

          Stacy wrote on October 30th, 2013
        • I hve tried IF and gained weight also.,.,im 48 yrs old and discouraged.,.,

          connie wrote on September 29th, 2014
    • 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

      Amy wrote on March 22nd, 2015
  3. If Mark ever figures out the difference between men and women I will accept religion and appoint him the one true God.

    Groktimus Primal wrote on June 19th, 2012
    • Re the difference between men and women: no man with half a brain is going to touch that one with a ten foot pole.

      rob wrote on June 19th, 2012
      • Isn’t ‘man with half a brain’ redundant?

        Women everywhere

        BillP wrote on June 19th, 2012
        • Funny! (though some seem to miss it…)

          John wrote on June 19th, 2012
        • 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! 😉

          em wrote on June 19th, 2012
        • 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!!

          John wrote on June 19th, 2012
        • @Tracy: Is the comment ‘man with half a brain’ sexist and inappropriate too? Or good for the goose but not the gander?

          Paleo Bon Rurgundy wrote on June 19th, 2012
        • sexist and inappropriate 😉 – remember sexism doesn’t mean (inappropriately) discriminating because of female sex, but any sex.

          Frederik wrote on June 20th, 2012
        • Not this woman. :) I love all the smart men out there, and respect them tremendously along with the women.

          Roberta Saum wrote on July 26th, 2012
        • Ouch!

          AS wrote on February 2nd, 2016
        • OMG STOP that is so damn funny!

          Mimi wrote on June 25th, 2016
      • 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?

        Michael wrote on June 19th, 2012
        • I meant “There are differences”

          Michael wrote on June 19th, 2012
    • 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.

      Julia wrote on August 15th, 2014
  4. “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.

    Brad wrote on June 19th, 2012
    • Amen!

      Nicole wrote on June 19th, 2012
    • 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?

      Tom Bassett-Dilley wrote on June 19th, 2012
      • 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.

        Bec wrote on June 19th, 2012
    • 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!

      Luke M-Davies wrote on June 19th, 2012
      • “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.

        Brad wrote on June 19th, 2012
    • 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.

      Roberta Saum wrote on July 26th, 2012
      • It’s great to hear someone else refer to it as, “the body.”

        Lindsay wrote on June 11th, 2014
  5. 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.

    vmckenna wrote on June 19th, 2012
    • 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.

      Debra wrote on June 19th, 2012
      • 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.

        Stefani wrote on June 19th, 2012
        • 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.

          jacquie wrote on June 19th, 2012
        • 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.
          : )

          Ma Flintstone wrote on June 19th, 2012
  6. 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.

    Jackie Kessler wrote on June 19th, 2012
    • string cheese? That is not food…

      cis wrote on July 12th, 2013
  7. 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.

    Nicole wrote on June 19th, 2012
  8. 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.

    new faster wrote on June 19th, 2012
    • 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

      Stefani wrote on June 19th, 2012
      • Interesting, thank you!

        new faster wrote on June 19th, 2012
      • 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 wrote on June 19th, 2012
      • 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.

        Lindsay wrote on June 20th, 2012
      • 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!

        Barb wrote on August 1st, 2012
      • guess i’m going to IF the whole of my exam period then!

        dill wrote on September 1st, 2012
      • My HGH increases during a fast, and I sleep like a baby. Burned off 2 1/2 lbs last night while I slept!

        Lisaloo wrote on October 16th, 2014
    • 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.

      Galina L. wrote on June 20th, 2012
  9. 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 :-)

    Carla wrote on June 19th, 2012
  10. 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!

    Saro Jane wrote on June 19th, 2012
    • 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…

      Erin wrote on June 19th, 2012
      • 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.

        Harry Mossman wrote on June 19th, 2012
        • 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.

          Schmaif wrote on February 24th, 2015
    • 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.

      Barb wrote on June 19th, 2012
      • 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.

        lynn wrote on August 3rd, 2012
    • 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.

      Shona wrote on August 25th, 2012
    • 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.

      SuzU wrote on November 15th, 2014
  11. 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?

    Michele wrote on June 19th, 2012
    • 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.

      Emily Mekeel wrote on June 19th, 2012
      • 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: and specifically for you I think in this post:
        And I recommend checking out the fertile thoughts forum,, 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.


        Stefani wrote on June 19th, 2012
        • 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…

          Michele wrote on June 20th, 2012
        • 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…

          Michelle wrote on July 3rd, 2012
    • 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?

      maybol wrote on June 19th, 2012
      • 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.

        Stefani wrote on June 19th, 2012
        • 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.

          Marlla wrote on June 19th, 2012
        • wow–that’s good to know!

          Jenny wrote on August 12th, 2012
    • 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!

      Gráinne wrote on June 24th, 2012
      • 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!

        Sharon wrote on December 18th, 2012
      • 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.

        AS wrote on February 2nd, 2016
    • 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.

      Lisaloo wrote on October 16th, 2014
  12. 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?

    Ryan Hand wrote on June 19th, 2012
    • 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.

      Stefani wrote on June 19th, 2012
      • 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.

        Laila Grace wrote on September 8th, 2015
    • 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!

      Tania wrote on June 19th, 2012
      • What your doing sounds similar to the GAPS diet. Don’t forget to eat bone broth.

        Paleo Bon Rurgundy wrote on June 19th, 2012
    • 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.

      Lisaloo wrote on October 16th, 2014
  13. 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.

    Lex wrote on June 19th, 2012
    • 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.

      Kayla wrote on June 19th, 2012
      • *my hair started falling out.

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

        Kayla wrote on June 19th, 2012
      • Waking up at 3 a.m. every morning is an adrenal fatigue (and possibly thyroid) symptom! (Read up at Stop the Thyroid Madness: 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.)

        Elenor wrote on June 21st, 2012
        • EXACTLY. I was just too lazy to explain it all. I’m very much in the beginning of fully healing.

          Lex wrote on June 22nd, 2012
    • 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.

      Stefani wrote on June 19th, 2012
      • 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!

        Ashley wrote on June 20th, 2012
    • 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 :).

      K wrote on June 19th, 2012
  14. 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.

    Shea wrote on June 19th, 2012
    • 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 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.

      Brick wrote on June 19th, 2012
  15. 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 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

    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. :)

    Stefani wrote on June 19th, 2012
    • “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%?

      secret agent girl wrote on June 20th, 2012
  16. 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.

    Lex wrote on June 19th, 2012
    • 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.

      Mark Sisson wrote on June 19th, 2012
      • 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.

        Lex wrote on June 19th, 2012
      • What are some signs that can help me determine if I am ‘fat adapted?’

        Alana wrote on June 19th, 2012
        • I’d like to learn this, too!

          secret agent girl wrote on June 20th, 2012
      • 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.
        I’d also be thrilled to talk about it more as I find it to be both fascinating and important.

        Stefani Ruper wrote on June 20th, 2012
        • 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.

          Lex wrote on June 22nd, 2012
        • I am wondering when you are speaking of these reactions to IF for women how long are the fasting states?

          Jodi wrote on June 27th, 2012
        • Hi Stefani,

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

          Jessica wrote on October 1st, 2015
      • 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.

        Jodi wrote on June 27th, 2012
    • 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.

      karen wrote on June 22nd, 2012
      • 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.

        SuzU wrote on March 27th, 2015
  17. 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.

    yoolieboolie wrote on June 19th, 2012
  18. 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.

    Diane wrote on June 19th, 2012
  19. 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! :)

    N3P3N7N3 wrote on June 19th, 2012
    • “WHEN”–here it is again! What does it stand for, please?

      secret agent girl wrote on June 20th, 2012
      • WHEN = When Hunger Ensues Naturally

        SouthernFriedBB wrote on June 20th, 2012
  20. 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.).

    Teresa wrote on June 19th, 2012
    • 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.

      Carla wrote on June 20th, 2012
  21. 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.

    Judy wrote on June 19th, 2012
    • 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.

      Teresa wrote on June 19th, 2012
      • Oops—that was supposed to be an additional comment for my previous post.

        Teresa wrote on June 19th, 2012
  22. 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.

    Doghug wrote on June 19th, 2012
  23. 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.

    MamaGrok wrote on June 19th, 2012
  24. opps :( it’s I’ll not a’ll
    sorry about that.

    Doghug wrote on June 19th, 2012
  25. 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.

    Happycyclegirl wrote on June 19th, 2012
  26. 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!

    qqemokitty wrote on June 19th, 2012
    • 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.

      Oceanside Grokette wrote on June 20th, 2012
  27. 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 :)

    Mikki wrote on June 19th, 2012
  28. 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.

    Vanessa wrote on June 19th, 2012
    • 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?

      secret agent girl wrote on June 20th, 2012
  29. 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.

    Christine wrote on June 19th, 2012
  30. 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!

    Abby J. wrote on June 19th, 2012
    • 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.

      Roberta Saum wrote on July 14th, 2012
    • 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.

      Roberta Saum wrote on July 29th, 2012
  31. 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.

    Ann wrote on June 19th, 2012
  32. 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.

    Becky wrote on June 19th, 2012
  33. Once again life made easier by Mark!

    Sangita wrote on June 19th, 2012
    • I’m not sure that skipping a meal twice a month is considered fasting? The article posted by Stefani from “” 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.

      Paleolady wrote on June 21st, 2012
  34. 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

    Monique DiCarlo wrote on June 19th, 2012
  35. 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.

    Cat wrote on June 19th, 2012
    • 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!

      Elenor wrote on June 21st, 2012
  36. 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.

    Audrey wrote on June 19th, 2012
  37. 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!

    Rachel wrote on June 19th, 2012
    • 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,

      Heather wrote on June 19th, 2012
  38. 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.

    Momto3 wrote on June 19th, 2012
  39. 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.

    Harry Mossman wrote on June 19th, 2012

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