The intermittent fasting approach to diet may go against everything you’ve heard about food, 
metabolism and muscle. But the research (not to mention the experience of many practitioners—including yours truly) has led me to believe this is one of the most effective dietary strategies you can utilize.
You may have grown up reading about the importance of small, frequent meals for “firing up your metabolism.” This was the bodybuilding dogma for decades and I also used to believe it.
But research has not demonstrated any metabolic difference in small, frequent meals versus large infrequent eating. One study, for example, compared the metabolic affect of two meals a day with eating seven meals a day in thirteen subjects. Researchers concluded there were “no consequences for the total 24 h energy expenditure (24 h EE) of the two feeding patterns.”1
Having said this, I’ll tell you two distinct advantages to an intermittent fasting approach to diet:
1. Simplicity/Compliance
Small, frequent meals are fine if this way of eating helps you consistently hit your daily caloric goals. But eating 6-7 times a day may not be practical for those of us who don’t make a living in the fitness profession.
I’ve also found low carbohydrate approaches to be very effective. But compliance is also an issue here—going several days without carbs is just kind of a pain in the rear end (memories of “keto breath” come to mind).
This is the beauty of intermittent fasting. It does take some getting used to, but you don’t have to stress over eating every few hours or completely abstaining from one type of food. This is important, because long-term compliance will be the most important factor in whether or not a diet “works.”
For me the adjustment to the diet kind of works in reverse to other things I’ve tried. In other words, it gets easier to do over time. It seems going for short periods of time without eating re-wires the brain and reduces compulsive eating. That’s been my experience, and many other practitioners attest to the same.
2. Hormonal
Some fear a short fast will slow the metabolism or put the body in “starvation mode.” But this doesn’t seem to be the case, either. A short fasting period will, in fact, maximize your fat burning potential. There are positive effects on growth hormone and catecholamines, both of which aid in fat loss.
Going longer periods without eating also causes the body to burn fat (vs. carbohydrates) for fuel. The study I cited earlier noted that subjects experienced increased fat oxidization when eating only two meals a day.
Some fear going without food will cause muscle loss, but this doesn’t seem to be the case. The bottom line is this: you will not lose muscle mass while dieting if you lift weights.
Resources/Programs
I’ll recommend three excellent resources if you are interested:
Brad Pilon’s Eat-Stop-Eat is a very well researched book for those who want a simplified approach to intermittent fasting. This is the one I’d recommend for those who want a beginner/basic guide–the plan only requires you to fast once or twice a week. It doesn’t mean you can eat everything in sight the rest of the time, but he explains that in more detail.
Jason Ferruggia’s Renegade Diet is a detailed plan to help you build lean muscle or lose fat, depending on your goal. One of the biggest advantages to his approach is the flexibility–you can adjust the diet to whatever phase of your training you happen to be working on.
John Romaniello’s Fat Loss Forever is a more advanced approach for those who want maximum fat loss results in minimal time. His plan calls eating most of your calories later in the day and making other adjustments (a “cheat day,” etc). This approach may surprise you if you’ve never tried it, but I’ve found it to be very effective (I used a similar approach to drop body fat).
Reference:
1. Eur J Clin Nutr. 1991 Mar;45(3):161-9. Influence of the feeding frequency on nutrient utilization in man: consequences for energy metabolism.
