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

    Kathy wrote on June 20th, 2012
  2. I have been experimenting with fasting the past year with great success. I have been coaching people using fasting as well. I can say from experience that for me fasting next to paleo has been the most positive change in my life for health and fitness. It allows me to eat massive and I mean MASSIVE meals while “dieting”. You can check out my results on this site actually as Mark posted my success story. Most of the women I do coach and advise have a much harder time with fasting then men. I recommend most do a shorter fast window of 10-12 hrs rather then the 14-16 I do my self. I train fasted and have gained muscle while losing body fat pretty easily. I do think it is a great tool if you love skipping breakfast and eating huge meals but I know alot of people men and women who love breakfast and like smaller meals and try to force themselves into fasting. Its supposed to make your life easier not harder : )

    Frank Sabia wrote on June 20th, 2012
  3. I am a 42 year old peri-menopausal woman who started the primal journey at 185 pounds (5’7″) and is now 143 pounds. I’m not wired for breakfast. I’m just not hungry until 10 am or later, so occasionally skipping dinner and then eating a late breakfast worked well in the beginning for energy level and fat loss. Now at the lower end of my weight, I notice that I feel weak and spacey. This also depends upon where I am in my cycle and how much protein intake I’ve had that week. I suspect that I have some adrenal fatigue, like a lot of folks. If this were balanced, fasting might feel better. The most important thing is to simply pay attention to your body.

    Christa wrote on June 20th, 2012
  4. I found this post discouraging, because I’m trying to fast each day til late afternoon, then eat. I tended to binge when I tried this the first time for a couple weeks approx. Not from hunger, but from food obsession. I’ve always had the food obsession, so that is one big plus for fasting during the day. It eliminates that obsession, and I don’t feel hunger. It eliminates thinking about food, making decisions about food, etc. A HUGE plus for me.

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

    Lynn123 wrote on June 20th, 2012
  5. This is timely as I am working my way up to doing a fast. First thing I tried was skipping breakfast if I wasn’t hungry.I realised how I had bought into the idea that you have to have brekkie and basically you have to eat every few hours or you will go into starvation mode. Thinking about that now, if that were true it would make humans very inefficient and unable to achieve much as they would have to stop to eat every few hours or – in theory – wake up in the night to eat.Sometimes I get up for work at 5am and I cannot face eating so I have enjoyed just waiting to see when I actually get hungry. At the moment I have not eaten for over ten hours. I’m not sure if I’m hungry!
    I always seem to get very hungry just before my period and during the first few days of it. Like I will feel like I am going to keel over. Last time I had this I had to have a Coke, nothing else would do, and I felt miles better.

    Polecatz wrote on June 20th, 2012
  6. I am female 5’6″ 130lb (lost 56lb 2.5yrs ago), 67yrs, so definitely post-menopausal.

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

    Marg wrote on June 20th, 2012
  7. I’m 42 and still fertile. I went Paleo about 10 months ago while in the midst of losing weight. Since going Paleo, I began to plateau, but that may simply be due to the fact that I’m down to the last 8 lbs and that’s never a quick loss. I started doing IF (and P90X) about 5 weeks ago. It’s been easy. I have definitely noticed the whole more-alert-and-energized thing, and thankfully have not had a problem with insomnia. But I’m happy to have read this post so I will know what’s up if this problem should appear. The IF has not really worked as a plateau-busting technique so far. On the other hand, I’ve gone from a size 6 down to a size 2. So it’s definitely doing something for me!

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

    Rachel B. wrote on June 20th, 2012
  8. I’m 44 years old with no sign of perimenopause. I have extremely regular periods which have become PMS-free since going Primal 2 years ago. Even as a kid, breakfast was revolting to me. I had zero appetite until midday.

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

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

    Janina wrote on June 20th, 2012
  9. I typically don’t eat first thing and always train on an empty stomach. However, my experiment with IF proved disastrous.

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

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

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

    Indiscreet wrote on June 20th, 2012
  10. 20 yr old overweight female here.

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

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

    Nixxy wrote on June 20th, 2012
  11. Lots of great thoughts on the subject of fasting. I have just found like some others on here that it diminishes my exercise experience. Even exercise that is more incidental to fun (rather than a program regimen). That down side is too much for me to do it. Can’t say that some of what people are saying on here hasn’t made me reconsider that position though. That is one of the beauties of this site.

    Cheryl Boswell wrote on June 21st, 2012
  12. Reading the comments I find it a bit of a shame that I didn’t try IF after starting primal but before I started hormone treatment.

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

    treborix wrote on June 21st, 2012
  13. I have been experimenting with 24-60 hr coffee and tea fasts with some remarkable results, thus far. There are still minor carb craving issues near the end, but those are eliminated more and more as triggers are discovered.
    IF is an extremely useful tool, and perhaps a minor crutch–albeit a sound one.

    wd wrote on June 21st, 2012
  14. 38 yo female, 5’10”, 150 lbs +- 10 lbs for the past 20 years. Former marathoner, primal (including exercise protocol) for 2 years.
    I practiced non-structured IF for the past year. (I ate only when hungry). This evolved into a feeding window of noon-7 pm most days, where the noon feeding was very light, working up to a good hearty (primal) dinner. I had never felt so good in my life! If primal food wasn’t available, I could go all day without eating and experience no discomfort. If I was particularly enjoying a certain meal, I would indulge a bit and eat a bit more than I probably needed. If I woke up hungry (rare) I would start eating earlier in the day. It all balanced out.
    Then I became pregnant and everything is out of whack. I don’t get hungry, but if I don’t eat every few hours I feel terrible. So now I am eating by the clock rather than by appetite and I feel all messed up diet-wise. I don’t enjoy food anymore because I am rarely hungry due to eating so frequently (hunger is the best seasoning).

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

    Kirstin J wrote on June 21st, 2012
  15. I’m 52 female peri?menopausal. I started 16/8 IFing about two months ago. I’ve leaned out even though I haven’t lost lbs. My energy and moods are good. Our 15yo granddaughter came to live with us last month = stress.
    My period has been regular; about 28-29 day cycle but last month I went 47 days between periods.
    I notice that I wake up at 3am and have trouble getting back to sleep. I was thinking that maybe it was just a normal primal split sleep pattern that Mark describes. Hearing about other women waking at 3am with IFing has me thinking that it’s time to experiment a little to determine what is true for me.
    Thanks to Mark and Stefani for sparking the conversation and to all that shared their experience.

    Lynn wrote on June 22nd, 2012
  16. I am 32, female, 5’8″, 145 (just happily put on 10 pounds in the past few months with a muscle-mass/strength-building program), the most regular periods ever (no birth control) and have enjoyed occasional IF, while eating mostly Paleo (definitely no grain, little sugar) the rest of the time. I tend to do 16-19 hours once a week or so and have had the same results of stable energy levels, and improvements in workouts — I actually tried IF as a way to shake a sort of rut/plateau in lifting. I especially like Mark’s comment about fasting when you need to — I’d rather do an unplanned fast than eat the unhealthy and overpriced offerings at the airport, for example.

    jessica wrote on June 22nd, 2012
  17. THANK YOU for this slap around the head – truly; I needed it.

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

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

    Sarah wrote on June 22nd, 2012
  18. Thanks so much for this post. I’m still a newbie to Paleo (coming up on one month)and I was never able to play around with IF before switching to Paleo, as I would get “the shakes” if I went too long without food and then I’d struggle not to binge. Since I started following a Paleo diet, I’ve been able to do short fasts for the first time. Ever. I’ve just dipped my toes into the water – skipping a lunch here, eating an early dinner and not eating again until late the next morning. But it was big for me, and I didn’t struggle, feel fatigued, hungry, or moody. Your blog has been a big motivator for me.

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

    Thanks so much for all you do!

    Stephanie wrote on June 23rd, 2012
  19. I’ve always alluded to the fact that women hormonally cant sustain on low carb. Ive written on my experience while IFing for 8-10 hrs, it would be stress inducing for my mind to relax and fall asleep. My first time going paleo, i lost my menstrual period for nearly five months, rough time getting any sleep which lead to late night food cravings, lost a lot head hair, grew more FACIAL hair, would get facial redness and drastic puffiness. The second i upped my carbs, my period returned. I will even admit i was much more healthier on a 80-20 vegetarian (but still wheatfree) diet than low carb. Men and womens sugar fasting levels are entirely different.

    jen wrote on June 24th, 2012
  20. I can’t do the IF thing either, and I’ve been Primal for over three years now. I’m 29 years old, 5’9″ and weigh 120 give or take a few pounds. I can skip breakfast once in a while, sure, delay meals because I’m not hungry, but I only made it 24 hours a couple times with some serious willpower on my part. Usually I hit about 18 and I’m like, “Good enough, where’s the food?!?!” I get lethargic, cranky, unmotivated, and hyper-focused on my next meal. As in, I’ll count down the hours until I’m allowed to eat. I don’t really think that’s the spirit of IF.

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

    Deanna wrote on June 24th, 2012
  21. I am 42 and can go for a 14 hour fast easily. 16 hours is a bit of a strech, but i can pull it of. I never fast voluntarily though, by following a plan or deciding it beforehand. I let it occur when it occurs naturally (It´s the WHEN method, I guess.)
    I never had any problems in skipping meals, quite on the contrary: it always makes me feel wonderful during the “fast” and also after breaking it.
    Planned fasts never worked for me. Not eating when I am hungry is a total trainwreck, physically and emotionally.
    To put it primally: if I am hungry and can´t get food, I have no problem in lifting (and tossing) heavy things! 😀

    Susanna wrote on June 25th, 2012
  22. Despite Stefani’s suggestions, I myself am an avid fan of IF. I’m a 26 yr old female, 5′ 6″, 118 and have had digestive issues my whole life. IF really helps mitigate most these issues (as well as living a paleo diet / lifestyle), but I have to say that IF is the icing on the cake. No hormonal issues or missed periods, in fact my body is more in tune with itself than it’s ever been. Definitely agree that it is good to self-experiment, do one’s research, etc. but Mr. Sisson your insight has been a big improvement on my own personal health and well being. Thank you!

    Rachel wrote on June 25th, 2012
  23. What IF does is takes one away from obsession with food…..if this is done regularly, like everything else, the body memory kicks in and says ok, now i can divert my energy to other activities beyond digestion…
    Unless one has a medical condition.

    jacquie wrote on June 26th, 2012
  24. Dear Mark,

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

    Varsha Tiwary


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

    EM wrote on July 3rd, 2012
  25. Hey all, I study fasting and wrote this up for another website. Here’s a blurb I wrote on why fasting doesn’t work that well for some normal women:

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

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

    MattyB wrote on July 4th, 2012
  26. I haven’t tried fasting–just not snacking feels like liberty to me, and I do get hungry at mealtimes. I’m only 6 months primal but I’ve been a low carb type 2 diabetic for going on 8 years. I have always eaten a little carb before I exercise, even at 5:30 am, because I had read that fasting exercise on top of the dawn effect can lead to higher and higher bg as the liver releases glucose but there isn’t enough insulin for the body to use it. Eating a small amount of carb is supposed to jump start the body to release insulin.

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

    Pamsc wrote on July 4th, 2012
    • I should add that I am 57 and postmenopausal.

      Pamsc wrote on July 4th, 2012
  27. I started eating primally in March, 2012 – I know I am new at this. I have not deviated from the lifestyle at all in that time, and feel at this point, I am a fat-burning beast! I have no cravings, and feel so good physically that I cannot imagine going back to consuming wheat or grains.

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

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

    Kat wrote on July 11th, 2012
  28. I am 36 year old female who stuggled with blood sugar in younger years. IF and weight training has been great for me. I listen to my body and don’t schedule the events. If I am not hungry I don’t eat breakfast. Weight training and running intervals are no problem. I have found I sleep better and have great energy on those days. Normal work outs are 30 to 40 minutes of intense training.

    Tracy wrote on July 13th, 2012
  29. Hello Mark,

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

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

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

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

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

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

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

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

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

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

    That was my experience with intermittent fasting.


    Roberta Saum wrote on July 14th, 2012
  30. Started fasting daily and I love it. I’m a 23 year old athletic female. I eat about 2000 cals in a 5 hour window. (I’m a monster I know..) and feel satisfied until the next day. I started with a bigger eating window at first. And my workouts suffered the first 3 days. But now I am so much stronger and have tons of energy throughout the day. I can do way more chin ups and push ups than before. I Sleep like a baby I am way less moody and finally didn’t pms this month. I don’t think I can go back to eating small meals. My mood has just been far too good. Please keep us ladies updated on IF for women.

    anon wrote on July 15th, 2012
  31. I suspect the level of testosterone matters. It varies from woman to woman. I think I have more than average as I put on muscle quickly. And I have no problem with IF, it worked great for me as a weight loss tool and my body adapted readily to it.

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

    Emma McCreary wrote on July 15th, 2012
  32. Thought I’d share my story…….. I’m a fit 37 YO and I found intermittent fasting pretty easy for the first few weeks and had lots of energy. i was doing a daily 16-18 hour fast and eating between 1200-1600 kcal/day. being 5’2″ I figured this was enough calories even though i do pretty heavy lifting 2-3 times/week and HIIT 2-3/week and have a lot of muscle mass. Well, after a few weeks I began to wake up ravenously hungry every morning (totally new for me) and find myself dizzy, low energy and grouchy by mid morning. then I began having obsessive food thoughts and cravings for treats. i eat a pretty clean paleo diet and never got below 17% body fat, but lost my period within 6 weeks of this program. clearly i need more calories and/or more regular meals!

    rachel wrote on July 16th, 2012
  33. Hi there,
    I am a 33 year old female athlete who has incorporated IF into my life since March of this year. I follow a 16/8 daily and also do one 24 hour a week. I mainly stick to lots of veggies and meat as well as fresh fruit (though usually only following a workout) so you could say that I am “fat-adapted”. I love IF. It has done wonders for me! I am 5’6″ tall and weigh 176 lbs and am about 18-19% body fat. IF has brought me to numbers I have never seen before in the gym ( 200lb bench press! 300 lb dead lift! 15 wide grip pull ups, while still maintaining a 25 min 5km run!!). It also has really helped in leaning me out. I can literally feel my body breaking down the adipose tissue in my abdominal area ( a real trouble spot for me!). Many other people have commented on my shape changing (I don’t notice it that much because I am constantly looking for results) But the best of all, I have constant energy throughout the day and that is very important as I am a partial-insomniac!! I do not crave food like I used to….when I am truly hungry, I know it. IF has also allowed me to identify a gluten sensitivity that I couldn’t nail down before. I recommend at least trying it, but remember it works best if you are fat adapted- if you stuff your face with pasta and bread for 8 hours, don’t expect to not be hungry for the remaining 16….your body loves carbs as it is an “easy” fuel,. Give yourself a chance and ease off on the carbs before you try IF… I think you will find it a lot easier to adjust. It took me about 3 days and then I just wasn’t thinking about food anymore!! I recommend it to all athletes! It is not difficult to maintain at all…I just get up, don’t eat, go to work and then eat lunch, back to work, hit the gym, come home and eat! Simple! Good luck everyone!

    Erica wrote on July 18th, 2012
  34. I am female, 54, post-menopause. I fast for about twenty or twenty-one hours on weekdays, entirely for the sake of convenience. I’m not an early-morning person, no matter what time I go to bed, and I have a long commute, so I don’t like to spend morning time cooking and eating breakfast.

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

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

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

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

    Valda Redfern wrote on July 18th, 2012
  35. Mark, I am a 35 year old female and have been doing IF. I usually do a 16/8 or a 20/5, and I feel great. I walk 4-5 miles a day (briskly) in a fasted state and lift weights several times a week. I was eating “healthy” and excercising but not losing the 15 lbs. I could never get rid of, so I tried IF and have finally been able to see results. Plus, I feel a lot calmer overall (less stress and anxiety) and realized I was obsessed with calorie counting and meal times before. IF has allowed me to be in tune with my body’s needs abd finally see results. My menstral cycle has not been affected nor has my sex drive. Thank you for your web site. It encourages me and gives me the necessary knowledge to get fit and lean plus feel better!

    Ali wrote on July 27th, 2012
  36. I have just starting IF, and I am fasting breakfast each morning and waiting until I’m actually hungry, around lunchtime instead of automatically eating breakfast first thing, the way I have done my whole life. I am also trialling fasting each Monday. This has been good (and easy)for me, but this week I tried a 2 day fast and woke up this morning (day 3) feeling absolutely terrible – weak and nauseous. I had a healthy breakfast and lunch and I’m starting to feel better now. I think a full one-day fast per week, and daily breakfast-skipping fasts are what works best for me. My body was certainly telling me off this morning! I lost 2kg in two days, which is probably a bit much! I only have a couple of kg’s to lose for my ideal weight anyway – only 1 more to go now!

    Andrea wrote on July 31st, 2012
  37. Oh, forgot to mention – I am 33 years old :-)

    Andrea wrote on July 31st, 2012
  38. Well id like to be able to fast, being a 25 years old female. But starving myself like that sends me into a panic, I just can’t do it. I previously suffered from Anorexia Nervosa and I associate food restriction with purposefully starving myself, so whenever I attempt to fast I find my body going into more than just a panic, it thinks Im ging to starve it again.

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

    Supercellbaebe wrote on August 6th, 2012
  39. I am certainly look at this as think my body (pre menopause) would not like the stress. We have just had this TV programme in the UK but that was a man doing a 2 day fast a week.

    EnglishRose wrote on August 8th, 2012
  40. Eating one meal a day has worked for me when nothing else would. And when I switched the timing of that one meal from midnight (I work late) to noon, I got even better results. It’s taken 3 years, but I’ve gone from 165 (where I’d been all of my adult life) to 130 lbs. I’m 5’7″ and age 57 and just got my first bikini!

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

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

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

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

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

    MyrrMade wrote on August 10th, 2012

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