The weight-loss world likes to describe our metabolism as an engine we have to rev throughout the day in order to burn through as much gas (a.k.a. calories) as possible. We’ve long been told that we can keep our metabolism fired up by eating right when we roll out of bed, and then frequently throughout the rest of the day. But if you’ve been forcing down breakfast before the sun comes up or lugging five square meals around with you for the sake of burning more calories and shedding fat, know this: The two theories behind this common advice are a little flawed.
The Thermic Effect Of Food
The first concept used to justify the idea that frequent meals ignite your metabolism is the ‘thermic effect of food,’ or TEF. TEF describes the spike in heat production (a.k.a. calories burned) that occurs in the body for up to eight hours after every time you eat—because it takes calories to digest food! On a given day, TEF accounts for about 10 percent of the calories you burn, explains Rob Danoff, D.O., director of the family residency program at Jefferson Health Northeast in Philadelphia. Hypothetically, if you could boost that TEF by eating more often, you could have a pretty significant impact on the total number of calories you burn, and thus, your metabolism.
While this idea sounds legit in theory, most studies have found no link between meal frequency and increased TEF. In fact, after examining four separate studies (in which people split the same total caloric intake among anything from one to seven meals), the International Society of Sports Nutrition found that increasing the number of meals consumed per day did not improve resting metabolic rate or 24-hour energy expenditure.
Ultimately, how many calories you burn digesting your food depends on how many total calories you eat, and what macronutrients (carbs, fat, protein) that food comes from, explains Spencer Nadolsky, M.D., diplomate of the American Board of Obesity Medicine and author of The Fat Loss Prescription. “As long your total calories and macronutrients are equal, your body will burn the same number of calories in the digestion process,” he says. So, regardless of whether you eat three 500-calorie meals (say one-third protein, one-third carbs, and one-third fat), or six 250-calorie meals with the same macro breakdown, you’ll burn the same number of calories processing your grub in the end.
If you really want to boost your TEF, what you can do is increase how much of your total caloric intake comes from protein compared to carbs or fat, since research shows that protein has the highest TEF of the three macros.
The other rational for eating frequent meals to keep your metabolism going is the idea that going too long without eating switches your body into ‘starvation mode,’ in which it stores calories it would otherwise burn.
While ‘starvation mode’ is, in fact, a real thing, it isn’t exactly an ever-present monster hiding in the pantry waiting to strike any time you go more than four hours without eating, says Wesley Delbridge, R.D., a spokesman for the Academy of Nutrition & Dietetics. “People think they’re going to go into starvation mode and halt their metabolism if they skip one meal, but that’s really not the case,” he says. “It takes longer than one day for the body to get to that point.”
Your body has plenty of fuel sources it can turn to—like the carbohydrates circulating as blood sugar or stored in your muscles and liver as glycogen, ketone bodies made from fats, and even protein from muscle tissue—when it doesn’t have any calories from food immediately available. Your body can last far longer than a few hours on these stored fuel sources before it has to start hoarding calories instead of burning them, he says.
In Defense Of Frequent Feedings
But wait, the plot thickens: Even though eating every few hours like clockwork doesn’t directly spike your metabolism, it might have indirect benefits that can still help you lean out.
First of all, one surefire way to boost your metabolism is to increase your muscle mass, since muscle requires a lot of calories every day to maintain. According to a review recently published in the Journal of the International Society of Sports Nutrition, optimal muscle gain requires loading up on protein a minimum of four times per day. So if eating more frequently throughout the day helps you get the protein you need to build muscle, it can ultimately help you rev your metabolism.
But that’s not the only way eating regularly can help you change your body. For example, research published in the Journal of the Academy of Nutrition and Dietetics found that people who ate frequent mini-meals were more likely to choose healthy foods and end up eating fewer calories overall than those who ate fewer, larger meals.
Why? “One of the biggest potential benefits of eating frequently is that it can help keep blood sugar levels stable,” explains Jessica Cording, M.S., R.D. “When your blood sugar dips, your brain sends you signals to eat more—so in theory, eating more frequently keeps those dips from happening, which then keeps you from eating more.”
In fact, when researchers at the Agricultural University of Athens had people with prediabetes or type 2 diabetes eat either three or six meals—but the same number of total daily calories—per day, the more frequent eaters experienced improvements in glycated hemoglobin and glucose levels (signs of blood sugar control), had fewer blood sugar and insulin spikes, and reported feeling less hungry throughout the day.
So even if eating smaller, more frequent meals doesn’t automatically power up your metabolism, it can be a major player in your fat-loss strategy.