Intermittent Fasting – Context Is Likely Important

Last week I was involved in two discussions on Intermittent Fasting (IF). One was extremely supportive of IF and the other highly critical. Both sides were represented by smart people and both made valid points. They each pointed to science to back up their position. Yet they completely disagreed with each other.

My view on fasting has changed a lot since 2007. I’ve gone back and forth along a spectrum of being anti-IF and pro-IF. I understand the arguments of both sides and at times I’ve been more swayed by one than the other. My personal experience has been varied.


Photo by Diana Robinson

Let me begin by saying that I am completely unqualified to comment on what happens at a cellular level. I have read experts and their opinions on the role fasting plays on cell repair (autophagy), metabolism and stress hormones. There is a lot of disagreement. I won’t step into those debates. Instead I will approach this debate as an incomplete information problem. In other words, approach this decision as an investor, which means hedging. I’ve written on this strategy in the post Approaching Nutrition From an Investor’s Mindset.

My general beliefs are:

  1. The person most likely to benefit from fasting is the person that doesn’t fast.
  2. The person least likely to benefit from fasting is the person either fasts too much, under eats, has a slow metabolism, exercises a lot, has poor sleep, or has a more stressful life. I am a believer in not stacking stressors. I cover this concept in the post Cold Exposure – Not One Size Fits All.
  3. Men are probably more likely to benefit than women. This is a common theme I’ve seen repeated across several blogs. And stocky men probably benefit more than lanky men.
  4. Fasting probably isn’t wise for children. I’m not a parent. Do your own research.
  5. The optimal amount of fasting is likely to be the least amount needed to make a positive change. This will be different for different people. And that amount will change for the individual. For some people that optimal amount is zero. For some it might be a cycle of on and off. Cycles might daily, weekly, monthly or even seasonal.

Instead of viewing fasting as good or bad, I think it makes sense to look at where the individual is at on their health journey. I want to share my story and how it changed between 2008 and today.

Stress is cited as the primary reason to not fast, but I believe it cuts both ways. There is a stress associated with never missing an eating window. Always cooking. Always grocery shopping. Always trying to make the best food decisions with time restrictions can be taxing. From the post Peat-atarians and Fear of Hormetic Stress:

Before discovering IF, I was a slave to hunger. Every 3 or so waking hours, I had to eat. IF taught me how to be patient with food. I learned how to cook, because I could now chose to eat later rather than immediately.

IF initially reduced my stress. I felt empowered. I learned I was stronger and more resilient than I had ever imagined. I cut way back on eating out and grabbing “nutritional bars” for quick calories and began discovering new foods that I could make in my own kitchen.

But then I made the mistake that many in the Paleo community did and that was take it too far. If a little is good, then more must be better? Nope.

In 2011, I did 70 consecutive days of Leangains, which is a 16 hour daily fast. During the 2nd month of the experiment I was often tired, always cold and I lost muscle. A few of his fanboys sent me emails or left comments on how it was my fault. I accepted some responsibility, but in the end I felt it was too much for me. My suspicion was confirmed when one my commenters Tauno found a old comment on the Leangains site from 2008 written by Berkhan.


This advice never made it into the 2010 Leangains Guide. Would I have done better with this strategy? Yes and I confirmed it later that summer. From my post Intermittent Fasting – Life After Leangains, I said this:

Since ending the daily 16 hour fasts, I have regained my strength and am now at the leanest point of my life. When I scaled back from daily fasts to 2-3 times per week, my metabolism kicked into gear and I started progressing again.

This was optimal for a while. Until I started losing too much weight. This was a problem that I solved and one of the tools I used was to stop fasting. Doing this increased my body temperature and increased my sleep quality. Both positive signs that I had made the right decision.


Pick Your Poison by Scott Ableman. When I am HUNGRY and away from my kitchen, I am a sucker for getting 3 tostadas from Taco Bell. That is 840 calories which has very little nutrition to show for itself. 🙁 

But I overshot my target weight and once again became a slave to hunger. With the stress of meal planning and not being able to always make good food choices, the quality of my diet got worse. Carrying around an extra 15 pounds has made me more lethargic, which hasn’t been good for my mood. To me this is my sign that it is time to start fasting again. Just a little. Maybe one 22 hour fast a week. I already know that my body can’t handle too much and I am aware of the symptoms (tired, cold, weak) if I were to push the fasting too much.

So is fasting good or bad? It was both for me. I no longer believe fasting is either magical or dangerous. Context is likely important.


Add yours

  1. I just watched these two videos from Diana Schwarzbein’s lecture at Silicon Valley Health Institute last night (hadn’t heard of Dr. Schwarzbein before yesterday), and the things she said her patients experienced sound familiar to me. Mostly, breaking down feels good until it doesn’t.

    Part 1:
    Part 2:

    Like you said, I think if you’re healthy, fasting won’t hurt, but if you’ve been broken down, fasting will make things worse.

  2. IF has always been my natural eating pattern, long before I knew it was a “thing.” I used to argue with my parents about eating breakfast and I stopped the minute I left home. I’m never hungry til lunchtime and then I am hungry through dinnertime. So I eat 2 meals plus a lot of snacks between about 2 and 8 pm. When on occasion I eat earlier (eg brunch with friends) it tends to kick start my afternoon hunger and I end up eating more through the day. So seems to work as a way of maintaining my weight. But I am struggling with being “skinny fat” and trying to tone up. Not sure what I should try in terms of tweaking eating times. I am 5′ 4″, 115 pounds, and eat low carb. Any more IF and I risk getting under-fed. Anyone with similar experience?

  3. I think if IF feels good then it’s okay. But I think a lot of people will not feel good while intermittent fasting.

    But too much fasting is bad news.

    When you initially reduce calories, your body goes through an anti-catabolic phase, or a prevention of body tissue break-down. The metabolism gradually compensates by using metabolically active tissue as energy – namely muscle tissue. Muscle tissue is catabolized in the form of deamination, surrendering intramuscular branched chain amino acids (BCAAs) for use as energy. If you eat less over a long period, you will burn less. Your body adapts by slowing metabolism. While slowing metabolism, your body signals your thyroid, leptin and other hormones, telling the metabolism to use less and less energy. Because lean tissue sacrifices BCAAs for energy use, your body goes into “hoarding mode,” so that it uses calories for storage and not to build lean tissue.

    Just keep this in mind before doing a long fast. And if your metabolism is already slow, as CM was sayin, now might not be the time to fast.

  4. @Diana – Thanks for sharing. Part 2 was informative. I like the using/building approach to understanding hormones and their relationship on metabolism. My habit of black coffee before food is probably not wise. 🙁

  5. Still listening to Schwarzbein videos — very long!

    And I checked out her website. An endocrinologist — very good. Interesting that she started work with advanced diabetic patients. So she’s on the “very very sick” side of the spectrum for health websites (as opposed to very, very athletic, like BBS). Don’t skip breakfast! she says.

    Me, I’m on the healthy side, so I’m breaking down and building up all the time. Last week, I did a 42-hour fast. Several days later, an intense HIT session on Sunday after which I ate like a demon. (Before the fast, on a 4-day business trip, I was over-eating in restaurants with clients.)

    MAS, I do admire the tone you are able to set on this site. People can participate without fear or baiting or trolling.

  6. Nice post. Yes, a lot of these body hacks work until they don’t, and everyone is different. There is a lot of myth-making out there: just do this and THIS happens! Like the granddaddy of them all, low-carb.

    Thanks for your ever-interesting blog!

  7. Here is an interesting and informative (IMHO) blog series on fasting:

    The context here is using fasting to reduce insulin resistance and reverse type 2 diabetes but may be of interest to others with an interest in health.
    I often skip breakfast when not hungry resulting in a16-18 fast but I do have some coffee w/ cream in the morning so I guess that technically breaks the fast. My IF along with HIT and a low carb diet have so far been successful in reducing excess bodyweight.

  8. The Schwarzbein video has me rethinking a few things. I’ve put a hold on her book at the library. If she is right, she makes a strong case for many not to fast. But there is context. I will be doing a follow-up post on her ideas. Those 2 hours could have been condensed to 20 minutes.

  9. @Gary – Thank you. I’ve learned a lot from the people that leave comments on this blog.

  10. @MAS Her second book is supposed to be the best. I skimmed her third book and thought it was just OK. Are you reconsidering fasting because she said rebuilding feels bad and you have been feeling less than great?

  11. @Diana – I want to go through her information more closely, but her explanations ring true to my “do the least necessary” that I posted above. For me the caffeine is a factor. If I have to choose between fasting and espresso, well you can guess which path I am going to take. 🙂 I do not think that more than one 22hr fast a week for me is going to be good. The question I need to figure out is if that is too much.

    I have holds on both The Schwarzbein Principle and The Schwarzbein Principle II. Those are the two my library has copies of.

  12. Very good article, MAS. Nice and balanced, to the point.

    I’d be very interested in a condensed version of the Schwarzbein stuff. I can’t see myself investing 2 hours, time is a precious commodity these days.

  13. @Øyvind – I will be doing a summary of the 2 hour presentation. I think I can tighten down the content to a few pages and combine them with my thoughts. Soon.

  14. Like MAS said, it’s about context. I had a great experience with fasting, low-carb and almost-raw foods.

    In 2010, i was 92kg of pure lard due to extreme bulking and decided go the extreme opposite way: eat only nature foods. In the morning, i did a semi-fast drinking a pineapple + kale juice (at the time, i was studying about the cruciferous vegetables and its anti-estrongenic effects). Then, on lunch, i ate meat light cooked on coconut oil or butter, unlimited kale and cabbage, olives, onion, and lots of extra-virgin olive oil. After, i drank six raw eggs straight from the glass (yes i had fear of not eating enough protein). Sometimes i had a big slice of pineapple to complete! Then dinner almost the same as lunch, but sometimes with sardines or chicken. I was using LOTS and i mean LOTS of salt, lemon and garlic with the foods.

    Due to water weight lost and the positive effects of not using carb as primary fuel, and lifestyle adjustments (sleeping at 10 PM due to circadian rhythm, cutting ALL sugar, ALL wheat, etc.), my six pack showed up in 30 days and i was sleeping like a king. From 10 PM to 06 and i literally jumped off the bed, no alarm, nothing, pure energy. I tought i had discovered the secret of the world and i was unstopabble. i was sprinting 15 minutes after waking up, for 15-20 minutes hard. At night, i did bodyweight exercises like a champion.

    Until the crash. Yes… it took a BIG toll on my body that i simple creashed and stopped sleep, then i lost muscle like a miserable, then my adrenals got so much burned that i simple abandoned all and started eating “normally” again. The transition was hard and even a slice of toast with milk gave me diarrhea.

    I then searched for effective alternative solutions for the low carb diet and found the best “diet” of my life: calories. I found it from one of most trusted fitness blogger, Matt Marshall. His 2-2-2-2 Method opened my eyes. I started with that and mixed with HIT and bodyweight, and today i’m great, sometimes the sleep is poor but it’s the life, daughter, my six month baby, etc.

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