Lyle McDonald said:Bellisle F et. al. Meal frequency and energy balance. Br J Nutr. (1997) 77 (Suppl 1):S57-70.
Several epidemiological studies have observed an inverse relationship between people's habitual frequency of eating and body weight, leading to the suggestion that a 'nibbling' meal pattern may help in the avoidance of obesity. A review of all pertinent studies shows that, although many fail to find any significant relationship, the relationship is consistently inverse in those that do observe a relationship. However, this finding is highly vulnerable to the probable confounding effects of post hoc changes in dietary patterns as a consequence of weight gain and to dietary under-reporting which undoubtedly invalidates some of the studies. We conclude that the epidemiological evidence is at best very weak, and almost certainly represents an artefact. A detailed review of the possible mechanistic explanations for a metabolic advantage of nibbling meal patterns failed to reveal significant benefits in respect of energy expenditure. Although some short-term studies suggest that the thermic effect of feeding is higher when an isoenergetic test load is divided into multiple small meals, other studies refute this, and most are neutral. More importantly, studies using whole-body calorimetry and doubly-labelled water to assess total 24 h energy expenditure find no difference between nibbling and gorging. Finally, with the exception of a single study, there is no evidence that weight loss on hypoenergetic regimens is altered by meal frequency. We conclude that any effects of meal pattern on the regulation of body weight are likely to be mediated through effects on the food intake side of the energy balance equation.
My comments: Ok, since nothing interesting came up on Pubcrawler this week, I decided that I'd crush another long-standing nutritional dogma (I thought about changing this from a research review to a mythbusting column but I'm going to run out of stupid myths to dismiss). 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 based on poor observational studies and direct research says that it's all false. The idea 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. So every time you eat, your metabolic rate goes up a little bit due to TEF. Aha! Eat more and metabolic rate goes up more, right?
Except, let's think about that. Say we have two people, both eating 3000 calories per day. One eats 6 meals of 500 calories/meal while the other eats 3 meals of 1000 calories/meal. 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. No difference. Sure, 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, it has to do with eating more food.
Which brings us, 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 later, maybe next week), they found no effect of varying meal frequency. None. 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. The study suggested that perhaps people who were overweight had started skipping breakfast in an attempt to lose weight; not that skipping breakfast made them fat.
That is, and in keeping with last week's study (and a lot of confusing issues regarding the effect of food on bodyweight/bodyfat), certain eating patterns tend to impact on caloric intake. 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. Other studies have shown that splitting one's daily calories into multiple smaller meals helps to control hunger: people tend to eat less when they split their meals and eat more frequently. When you go too long between meals (I usually find that 3-5 hours is about the limit depending on the meal composition), you tend to get hungry and end up at the vending machine eating candy. Eating more smaller meals can also have some health benefits in terms of blood glucose control and blood cholesterol; no-one is denying that.
However, this is all tangential to the claims being made for metabolic rate. Whether you eat 3 meals per day or 6, if your daily caloric intake is identical, you will expend the same number of calories per day from TEF. And, as opposed to mice and rats, for whom everything happens faster, skipping a meal will not affect human metabolic rate at all. Quite in fact, it takes at least 3-4 days of fairly strict dieting to impact on metabolic rate; a single meal means nothing. You will not go into 'starvation mode' because you went more than 3 hours without a meal.
More practically, I sometimes wonder if the people who are adamant about 6 meals/day have ever worked with a small female athlete or bodybuilder. A 120 lb female may have a daily food intake of 1200 calories/day on a diet. Dividing that into 6 meals gives you 200 calorie 'meals'. More like a snack. 4 meals of 300 calories or even 3 meals of 400 calories is a much more livable approach than a few bites of food every 3 hours. The low caloric intake on my Rapid Fat Loss Handbook more or less prevents a 6 meal/day approach, each 'meal' ends up being nothing. I recommend 3-4 meals/day on that diet.
So, like last week's research review about the glycemic index, quit obsessing about meal frequency if it doesn't fit easily into your lifestyle. I consider 3-4 meals/day a workable minimum for most, 3 meals plus a couple of snacks works just fine too. High meal frequencies may have benefits under certain conditions but are in no way mandatory. And, in case you missed it the first time through: eating more frequently does NOT, I repeat DOES NOT, 'stoke the metabolic fire'.
Straight from the expert (minus a few edits on my part for profanity; Lyle is a vulgar guy to say the least).
