Alternate Day Fasting: Not For Everyone?

I’ve been doing alternate day fasting for about two months. I find it very easy. In several ways it’s easier than eating every day:

  • save time
  • save money
  • less constrained on eating days
  • a little more hungry than usual on fasting days (up to a point hunger is pleasant — when the Shangri-La Diet wiped out all my hunger, I didn’t like it)
  • sense of accomplishment when I wake up after a fasting day (I did it)
  • food tastes better

Maybe my friends are unusually tolerant but I have yet to encounter a serious negative. Yesterday, a fasting day, I happily watched a friend eat dinner. I had two bites out of curiosity. I saw nothing to suggest it made her uncomfortable I wasn’t eating.

However, a different friend has told me that alternate day fasting made her sick. She did it for about three months, felt worse and worse, and finally stopped. She believes it works less well for women than for men. I suspect a heavy exercise routine (she ran a lot) made alternate day fasting more difficult. But there is also the best-selling book The FastDiet. It has two authors, a man (Michael Mosely, a doctor) and a woman (Mimi Spencer, a journalist). The book contains a remarkably short and remarkably unenthusiastic description of Spencer’s experience with intermittent fasting. Maybe it didn’t agree with her, either.

9 Replies to “Alternate Day Fasting: Not For Everyone?”

  1. There are many comments on various paleo blogs indicating that intermittent fasting is more difficult and less beneficial for women.

  2. I have seen several discussions on “paleo” blogs that suggest fasting – intermittent, alternate day, whatever – isn’t always good for women, and some suggest it’s never good.


  3. I fast one or two days a week. I like it so far. I feel better and with more energy the next day. I don’t exactly feel great on fast days. I don’t think that I could do two consecutive days, much less alternate days. I can’t run much on the days I fast. It feels like it would be too much stress on my body.

    By the way, the 5:2 authors don’t always recommend fasting two consecutive days. And don’t forget that they define fasting days as days in which men are advised to consume 600 calories and women 500. That’s very different from alternate day fasting with no (or few) calories on fasting days.

  4. I tried 5:2 for a couple of weeks. Initially I did great, but after maybe 6 weeks my stomach started protesting. Violently! I switched back to normal eating and it took me about 2 months before the stomach got back to normal. (I had the impression that too much nightshade plants in my diet caused the upset)

    I will try 5:2 again as I really like the concept and I do want to know if this was just a one time fluke or not.

  5. I believe its individual.

    For me, fasting has been terrible for awhile. I simply could not stand it. Not psychologically – physically. It would drain my energy and make me sick.

    then it changed. now i can fast.

    For a very long time, I was unable to fall asleep without having eaten some time before sleep.

  6. When I investigated alternate day fasting several years ago, I discovered that 1) not enough investigation had gone on that explored the differences male vs female physiology made on the effects of fasting, and 2) what findings were available re: female fasting weren’t so good. It makes sense; during times of scarcity, it’s harder on a female body (and on the developing fetus) to be pregnant. Negative changes in women appeared to be more pronounced and possibly linked to hormonal balance. We do know that, under a certain body weight, fertility can be affected and menses can be delayed or halted. Anecdotal evidence in some of the fasting forums I read also seemed to also point to fasting being unhealthy and not beneficial for some women (though some of those poor women would try repeatedly, experience the same negative results and feel that they were failing). The potential benefits (possibly mainly experienced by males) didn’t sound worth the potential risks, to me.

  7. As someone who has worked with a lot of performance athletes, attempting to fast while training for performance can put down a beating on the adrenals. Women are indeed more susceptible to dysfunction in the adrenal/thyroid/ovary axis. Not to say that fasting can’t be done for performance athletes, but it usually needs to be a very resilient person with a good understanding of how to fuel during their non-fasting periods.

    Fasting may also exacerbate adrenal and thyroid issues in people just interested in health and fitness, so, for someone who’s already started down some paths of hormonal issues, fasting can dig their hole a bit deeper. Again, not to say that it can’t be done or that it’s not beneficial, just some folks are way more susceptible to downregulating their thyroid and screwing up their cortisol curve.

  8. Here is Mimi Spencer’s experience with the Fast Diet (page 9):

    “In the months that I wrote the Times feature, I have remained a convert. An evangelist, actually. I’m still “on” the Fast Diet, but I barely notice it. At the outset, I weighed 132 pounds. At five feet, seven inches, my BMI was an OK 21.4. Today, as I write, I weigh 119 pounds, with a BMI of 19.4. That’s a weight off. I feel light, lean, and alive. Fasting has become part of my weekly life, something I do automatically without stressing about it. Six months in, I have more energy, more bounce, clearer skin, a great zest for life.”

    Accounting for British understatement, and overlooking the excessive comma usage, I would say that is a strong endorsement.

    Seth: One paragraph…in a whole book? What about lab results? What about blood sugar? What about examples of feeling “light, lean, and alive”? Did she recommend the diet to anyone else? This isn’t my idea of enthusiasm.

  9. It’s 11:17pm. I haven’t eaten all day. I suspect that the cooking and eating time saved was replaced by time spent, especially as the day wore on, fantasizing about my next meal, and Googling recipes for breakfast. No euphoria yet.

    Seth: I think the “conditioned hunger” goes away but the saved time does not.

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