My Comments
Perhaps one of the longest standing dogmas in the weight loss and bodybuilding world is the absolute necessity of eating frequently for various reasons. Specific to weight loss, how many times have you heard something along the lines of “Eating 6 times per day stokes the metabolic fire.” or “You must eat 6 times per day to lose fat effectively.” or “Skipping even one meal per day will slow your metabolic rate and you’ll hoard fat.” Probably a lot
Well, guess what. The idea is primarily based on awful observational studies and direct research (where meal frequency is varied within the context of an identical number of calories under controlled conditions) says that it’s all basically nonsense. The basic premise came, essentially out of a misunderstanding of the thermic effect of food (TEF) also called dietary induced thermogenesis (DIT) which are the calories burned in processing of the food you eat.
While TEF differs for the different nutrients, on average it constitutes about 10% of a typical mixed diet (this varies between nutrients and slight differences may be seen with extreme variations in macronutrient intake). So every time you eat, your metabolic rate goes up a little bit due to TEF
Aha! Eat more frequently and metabolic rate goes up more, right? Because you’re stimulating TEF more often. Well, no. Here’s why:
Say we have two people, both eating the same 3000 calories per day from identical macronutrients. One eats 6 meals of 500 calories/meal while the other eats 3 meals of 1000 calories/meal and we’ll assume a TEF of 10%. So the first will have a TEF of 50 calories (10% of 500) 6 times/day. The second will have a TEF of 100 calories (10% of 1000 calories) 3 times/day. Well, 6X50 = 300 calories/day and 3X100 = 300 calories/day. There’s no difference.
Of course, if you increase food intake from, say, 1500 calories to 2000 calories, you will burn more with TEF; but this has nothing to do with meal frequency per se, it has to do with eating more food. I only bring this up because I’ve seen people (try to) argue the positive effect of TEF by dredging up studies where folks ate more total calories. Of course TEF goes up, but not because they are eating more frequently; rather it’s because they are eating more food in total.
I want to address that last bit a little bit more since the fact that TEF goes up with increasing food intake is often used to argue that “metabolism chases intake” and to make arguments for eating more to get lean. Here’s the problem with this ‘logic’. Assuming an average 10% TEF, increasing food intake from 1500 calories to 2000 calories per day will increase caloric expenditure by 50 calories. But you had to eat 500 more calories to get it. So even if you burn 50 calories more, you’re still consuming 450 more calories than you would have otherwise. Basically, the logic is akin to saying “I saved $100 by spending $1000 because what I bought was 10% off”. Right, but you’re still out $900 that you wouldn’t have spent and you’d have saved $1000 if you hadn’t bought it in the first place. The same logic applies here.
Which brings me, the long way around, to the above review paper which examined not only earlier observational work but also direct studies of varying meal frequency on either weight loss (during such studies) or metabolic rate. And, with the exception of a poorly done study on boxers (which I’ll discuss a bit below), they found no effect of varying meal frequency on any of the examined parameters. No increase in metabolic rate, no increase in weight loss, no nothing. What’s going on?
They concluded that earlier studies finding an effect of meal frequency on weight gain (or loss) had more to do with changes in appetite or food intake, not from a direct impact on metabolic rate. For example, early observational studies found that people who skipped breakfast were heavier and this still resonates today with the idea that skipping breakfast makes you fatter. However, the review points out that this may be confusing cause and effect: people often start skipping meals to lose weight.
I’d note, tangentially and I’ll come back to this below, that there is no data in humans that skipping a single meal or even a day’s worth of meals does anything to metabolic rate. Human metabolism simply doesn’t operate that quickly and various research into both fasting and intermittent fasting show, if anything, a slight (~5% or so) increase in metabolic rate during the initial period of fasting. The idea that skipping breakfast or a single meal slows metabolic rate or induces a starvation response is simply nonsensical.
Basically, there are a lot of confounding issues when you start looking at observational work on diet and body weight. As I discussed in detail in Is A Calorie A Calorie, you often find that certain eating patterns impact on caloric intake. And it’s those changes in caloric intake (rather than the eating patterns themselves) that are causing changes in weight
For example, some early studies actually found that eating more frequently caused weight gain, mainly because the foods being added were snacks and were in addition to normal food intake. In that situation, a higher meal frequency led to greater food intake and weight gain. But it wasn’t the meal frequency per se that caused the weight gain, it was the fact that folks were eating more.
But yeah I guess I'm pretty traditional--breakfast, snack, lunch, snack, dinner. SOMETIMES dessert 
