I am now wrapping up my first week with IF and honestly, I love it. For me, (so far) this works. I feel satisfied, and I feel I have much, much more control over food (I can’t explain this, I just do). I am truly enjoying healthy foods, but am not worrying about calories. My friend who asked me about it last week is also loving it.
She feels she has more energy, feels she is spending less time worrying about what to eat, and is craving vegetables. I think there is a lot going on with IF that we don’t understand. Not a lot of studies have been done on this method of eating, and depending on which approach you take, there are other things besides the fasting that can be playing a part. But in the end, it doesn’t really matter, as long as you feel good.
In reality, we are all practicing a form of IF. Intermittent fasting, in it’s most simple form, is simply alternating periods of eating with periods of fasting. So from the time you stop eating at night until you get up in the morning and start eating again, you are practicing a form of IF ~ you are fasting while you sleep. For most people this fasting period is around 12 hours. With IF, this fasting period is extended. How long it is extended depends on which method you follow. Essentially there are 3 fasting windows that have been promoted by different people ~ 24 hours, 20 hours and 16 hours. The 24 hour fast is popularized by Brad Pilon, author of “Eat, Stop, Eat.” This method is probably the simplest ~ one day (or two…more on that later) you fast…the entire day. You do this every week (or you can cycle, e.g. 3 days of eating to 1 day of fasting, ignoring actual weeks). There aren’t a lot of rules around this method, other than to fast for 24 hours. It allows you to eat breakfast on the days you aren’t fasting. For some people, this could work very well. In an interview Brad did with Nia Shanks (see here) he states
…the concept behind Eat Stop Eat…is that one or two 24 hour breaks from eating per week when combined with resistance training can be an unbelievable easy and effective way to lose body fat without losing muscle mass.
Brad also talks about how the 24 “break from eating” changes your relationship with food…this is really what I have been noticing myself in my short period of time trying IF (although I am not doing the 24 hour fast method):
When you first start fasting you really learn WHY you eat. It has so much to do with simple cues and habits, and so little to do with hunger, this revelation is amazing for so many people and it’s valuable information that can help you eat better during the times you are not fasting.
I agree 100%. For me, however, the thought of fasting (or as Brad likes to now call it, “taking a break from eating”) for 24 hours each week sounds a bit overwhelming. I have never fasted for 24 hours. Not for medical purposes, not for religious purposes, never. 24 hours without food? Really? Yes, it’s simple, but I’m not sure I’m capable of doing that.
Enter option two, the 16 hour fast. This method is popularized by Martin Berkhan of Leangains. This method has men fasting for 16 hours and eating (generally 3 meals, but there are no rules about this) during an 8 hour window. Women are instructed to fast for 14 hours. Exercising is a part of this method of eating. While Martin feels that there are benefits to exercising in a fasted state, he acknowledges that not everyone can work out at noon and eat at 1; as a result, he has methods for those who workout at different times of the day. And while he suggests that your fast start at night and continue until lunch, this is also flexible, depending on your own schedule…he just thinks that for most people, eating at lunch and dinnertime is easier to do.
Martin’s method is more complicated than the 24 hours fast in that it includes both carb-cycling & nutrient cycling. How much of this you follow is up to you, but understand your results might be different if you don’t subscribe to this. Carb-cycling essentially means that carb intake should follow a workout; nutrient cycling means that you take in more calories on workout days, fewer calories on non-workout days. Since I workout 5-6 days a week, I am trying to eat my carbs on my lifting days (3 days a week) as I feel those are my “intense” workout days. I am also following a 16 hour fast/8 hour feed window as opposed to the 14 hour fasting window Martin suggests for women. I am doing this because for me I didn’t feel like adding 2 hours to my usual fasting window of 12 hours seemed like that much of a change. I also think that for me, having a shorter period of time in which to eat helps me to keep my total calories under control.
Overall, I feel the 16 hour fast method is easier for many people, but it also means you never eat breakfast (that doesn’t mean you can’t have breakfast food, it only means you aren’t eating it in the morning). For some people this might be a difficult thing to give up. In addition, if you follow Martin’s method strictly, it is much more complicated than the 24 hour fast method.
The third and final method I want to share with you is the 20 hour fast/4 hour feeding window popularized by Ori Hofmekler called the Warrior Diet. Truthfully I know the least about this method, so I will share with you something pulled from the Warrior Diet website:
Warrior Diet Principles1. Eat One Main Meal at Night
There is evidence that humans are nocturnal eaters, inherently programmed for undereating and toiling during the day, followed by overeating and relaxing at night.2. Go Low on the Food Chain
Researchers believe that the human genome is programmed for a late Paleolithic world. As hunter/gatherers we’re better adapted to pre-agricultural food– i.e. chemical-free fruit, vegetables, roots, sprouted legumes, nuts, seeds, fertile eggs, marine food (wild catch), and dairy from grass fed animals.3. Exercise While Undereating
It has been established that we are inherently carrying survival mechanisms that benefit us when triggered by physical or nutritional stress such as exercise or undereating. Combining exercise with undereating will amplify the beneficial mechanisms of both – increasing our ability to utilize energy, improve strength and resist fatigue.

Different strokes for different folks.

Hello Lisa,
Thanks for this blog. Do you think the 16hr fast is a good idea for in full training mode 1/2 ironman training? I like what you wrote, but I was just wondering what you think about applying this to high end endurance type athletes. Thanks.
Best,
Brian D.
I can’t say I’m qualified to really answer that. I think in the e-book by John Berardi there is some reference to the fact that you might need to modify for endurance type training. The idea of training while fasted isn’t so difficult if you are doing an hour of strength training or some other such activity, but going out for 3 hours is different. Also understand that Martin Berkhan, the Leangains “founder” prescribes taking BCAA’s (branched chain amino acids) before, during and after training, which is supposed to help with the idea of training fasted. I haven’t tried that, and have generally felt fine training fasted. Margaret, too, has been doing okay with it, but remember we are talking an hour workout or so.