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

    Susan wrote on June 20th, 2012
  2. for Marks “study” purposes: 53 YO PM female. When I first went primal, I seemed to “effortlessly” (its always an effort for me – but weight was consistent for 3-4 years) be able to maintain a very lean 132, about 20 bmi, 15% (VERY correctly measured DEXA) body fat. Over the past year, my weight has creeped up. My hypothesis is that the scarcity signals are overwhelming what was already an intentional hormetic way of eating, as I gain/maintain weight at my theoretic/calculate lose a pound a week level. I added the IFing for 18 to 24 hour periods, and intensified training with greater emphasis on Tabata-style. I like the cold water swimming, but by the temporary increase in blood glucose, I suspect it is also fairly stressful.My body temp really seemed too low (rarely/never at 98.6), so now I’m tracking to better understand what impacts it. Because I’m always playing with so many variables, its a little hard to say what causes what, so I’m trying to really focus on quantifying as many measurements as possible. It may be as simple as just eating more calories:-). I am using Cronometer to try to keep myself honest, but it is pretty easy to be in “denial.” That it was a tsp of fat vs. a tablespoon, etc.

    deb b wrote on June 20th, 2012
  3. 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
  4. 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
  5. 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
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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
  12. 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
  13. 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
  14. 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
  15. 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
  16. 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
  17. 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
  18. 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
  19. 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
  20. 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
  21. 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
  22. 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
  23. 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
  24. 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
  25. 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
  26. 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
  27. 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
  28. 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
  29. 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

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