I recently wrote about the lack of scientific support for the theory that you should reduce carbs at night . In the same spirit (and by popular request), I thought I’d take the time to tackle another common nutritional theory. Namely, the claim that eating small, frequent meals stokes your metabolism.
I’m sure you’ve heard this one before. Bodybuilders and nutritionists have long preached that spacing out food consumption over five to six small meals a day is optimal for losing body fat. For years I too adhered to this belief. A wealth of emerging research, however, changed my viewpoint.
The strategy to eat small, frequent meals is based on the belief that when you go without eating for more than a few hours, your body senses deprivation and shifts into a “starvation mode.” Part of the starvation response is to decrease resting energy expenditure. In effect, the body slows down its metabolic rate to conserve energy. It’s a logical theory but alas it doesn’t seem to translate into practice, at least in the short-term (i.e. over about a 24 hour period or so). As such, the vast majority of studies examining metabolic rate have failed to show a clear advantage for increasing meal frequency.
On a similar note, the thought that frequent eating enhances the thermic effect of food (TEF)–a measure of the energy expended during digestion–is also flawed. A simple example should make this readily apparent. Let’s say you eat an 1800 calorie diet that averages a 10% TEF. If you space out meals equally so that you eat six times a day, the TEF would look like this:
Meal 1: 300 x .10 = 30
Meal 2: 300 x .10 = 30
Meal 3: 300 x .10 = 30
Meal 4: 300 x .10 = 30
Meal 5: 300 x .10 = 30
Meal 6: 300 x .10 = 30
Add up the numbers and total expenditure through the TEF will be 180 calories. Now let’s look at the same scenario except eating three times a day rather than six:
Meal 1: 600 x .10 = 60
Meal 2: 600 x .10 = 60
Meal 3: 600 x .10 = 60
Do the math and you’ll see it’s the same 180 calories expended through the TEF. This holds true regardless of how many times a day you eat.
Okay, so perhaps you want to focus on the benefits of more frequent meals on appetite. This is supposedly related to the effect of eating frequency on hormones. For one, it is claimed that large meals cause insulin spikes, which switch on various mechanisms that increase fat storage. The spikes then lead to a crash, where there is a tendency toward hypoglycemia (low blood sugar). Hunger pangs ensue and you invariably end up binging out. For another, an absence of frequent food is thought to increase the secretion of a gut hormone called ghrelin. Ghrelin is referred to as the “hunger hormone.” It exerts its effects by slowing down fat utilization and increasing appetite. Without consistent food consumption, ghrelin levels supposedly remain elevated for extended periods of time, increasing the urge to eat.
Frequent meals are purported to counteract these negative effects on hormones. Blood sugar is supposedly better regulated and, because there is an almost constant flow of food into the stomach, the hunger-inducing effects of ghrelin are suppressed, reducing the urge to binge out. Sounds logical, right? Sorry, another instance where logic and reality don’t mesh. Recent studies by Leidy et al. (1, 2) found no difference in appetite in those who consume six meals compared to three. Interesting, the researchers actually showed an increased satiety when the three-meal-a-day group followed a higher protein diet! On the other hand, consuming fewer than three meals a day does seem to have a negative effect on appetite (3), suggesting that this may be the minimum number of daily meals that need to be consumed from an appetite-control standpoint.
But what about body fat? Surely eating more frequently has to increase fat loss by some mechanism. Not! Provided calories are controlled, fat loss is similar between three-meals-a-day versus six-meals-a-day (4) A recent review paper (5) actually found that intermittent fasting–where people abstain from eating for upwards of 24 hours at a time–was equally as effective as caloric restriction in promoting weight loss. Read this again. The fasted subjects didn’t eat for an entire day at a time and still lost weight to a similar degree as those who ate daily meals. Apparently the starvation response is a lot more complex than some will have you believe.
A recent position statement by the International Society of Sports Nutrition covered the subject of meal frequency in detail. I’d highly recommend that you check out Alan Aragon’s critique of this paper for an in depth analysis.
In sum, current evidence doesn’t support the contention that eating more frequently enhances fat loss. Provided you eat a minimum of three meals a day, there does not seem to be any difference if frequency is increased beyond this number. Now this doesn’t mean that eating more frequent meals is a bad thing. I actually prefer a “grazing” schedule and have found it to be an effective eating strategy for my lifestyle. This is a personal choice that works for me. Others might find eating three times a day to be more appropriate.
The most important important factor here seems to be maintaining a regimented eating program–those who keep to a schedule see better results than those who don’t. It also should be pointed out that the majority of research studies have evaluated overweight subjects. Might more frequent meals help to strip away that last pound or two of body fat in otherwise lean individuals? As they say, further research is needed…
1) Leidy HJ, Tang M, Armstrong CL, Martin CB, Campbell WW. The effects of consuming frequent, higher protein meals on appetite and satiety during weight loss in overweight/obese men. Obesity (Silver Spring). 2011 Apr;19(4):818-24. PMID:
2) Leidy HJ, Armstrong CL, Tang M, Mattes RD, Campbell WW. The influence of higher protein intake and greater eating frequency on appetite control in overweight and obese men. Obesity (Silver Spring). 2010 Sep;18(9):1725-32.
3) Leidy HJ, Campbell WW. The effect of eating frequency on appetite control and food intake: brief synopsis of controlled feeding studies. J Nutr. 2011 Jan;141(1):154-7.
4) Cameron JD, Cyr MJ, Doucet E. Increased meal frequency does not promote greater weight loss in subjects who were prescribed an 8-week equi-energetic energy-restricted diet. Br J Nutr. 2010 Apr;103(8):1098-101.
5) Varady KA. Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss? Obes Rev. 2011 Mar 17.