"Years ago, we all believed that you needed to eat multiple times a day to keep your metabolism stoked. ... You had to keep feeding the fire and keep the furnace burning. But that theory goes back and forth, and newer research is showing that it really doesn't slow metabolism if you're not eating multiple times a day," said Martha McKittrick, a registered dietitian in New York City who has provided weight-loss counseling for over 20 years.
And despite the notion that eating more often means more opportunities to burn calories, thanks to the energy involved in digesting, absorbing and metabolizing food's nutrients, research suggests
that doing so does not appear to significantly enhance metabolism or total calories burned.
"In the '80s, grazing was thought to be an optimal way of losing weight ... but human studies did not support this at all," said David Levitsky, a professor of nutrition and psychology at Cornell University who has researched the topic of meal frequency and its effects on calorie intake. "It was thought that if you ate more frequently, the amount of calories you retain would go down, and more calories would be burned. But controlled experiments in humans show that there is no metabolic advantage to eating 12 smaller meals versus eating three or four meals per day, with the same total number of calories."
Other experts agree. "Meal frequency does not affect metabolic rate and thus has no direct effect on weight loss," said Carla Wolper, a registered dietitian and nutrition consultant at the ColumbiaDoctors Executive Health assessment program who spent 25 years on the nutrition faculty at the New York Obesity Nutrition Research Center.
In fact, some research suggests that eating even fewer than three meals may be best in terms of controlling calories: In one study
, when individuals skipped breakfast, they consumed about 400 fewer calories for the entire day compared to when they ate breakfast.
"If you decrease the number of occasions to eat, your total calorie intake goes down," said Levitsky, who authored the study. "People think if you skip breakfast, you will overeat later ... and that doesn't happen. Your intake goes up, but not nearly as much as the amount that you skipped."
An eating pattern for every body
So should you give up on a diet plan of six or more mini-meals, spaced a few hours apart? Not necessarily. The optimal timing of eating may depend on various factors unique to each individual.
"Some folks are grazers by nature, so six small meals might be more in line with their natural inclinations. Other folks eat by the clock, at 7 a.m., 12 p.m. and 6 p.m., for example. The real issue regarding temptation at mealtime is planning. If people have a great food plan, they will probably do well," Wolper said.
McKittrick agrees. "Some are grazers; some are meal-eaters. ... It's fine if they graze, but make sure calories are controlled so it's not an ongoing graze-fest."
The case for small, frequent meals
While some may enjoy sitting down to three meals each day, others may find that it's just too much food at once.
"Some people don't have huge appetites. ... If they have a 600-calorie sandwich, they may have half at noon and eat the other half at 3 p.m.," McKittrick said. "Eating large meals may also make them tired ... so they're better off with small frequent feedings because it promotes more stable blood sugar and they get more energized."
One's daily routine may not allow for the opportunity to take a big lunch break -- and so a grazing style of eating is a better fit.
For a new mom, eating three meals a day can be particularly challenging. "Lots of mothers spend so much time with their kids that they can't sit down and have a full lunch ... so eating more frequently better suits their lifestyle," McKittrick said.
Health issues may also dictate which style of eating is best. For example, people who have diabetes or hypoglycemia (low blood sugar) can feel shaky, tired and weak if they go too long without eating, so six small meals may be best. Those who have other health conditions including gastroparesis, irritable bowel syndrome and acid reflux may feel better by eating small meals spaced three or four hours apart. The same may be true for seniors.
"A lot of seniors can only have a piece of toast and an egg, and then they get full. As you get older, you just don't have as much of an appetite, and you feel full more quickly," McKittrick said.
The case for three bigger meals
Experts say that eating more frequently may be problematic for those who have trouble with portion control or something known as stimulus-bound eating, when the sight of a specific food prompts you to eat it, which can lead to weight gain.
"The bulk of the evidence suggests that humans are opportunistic eaters ... and if we are given more chances to eat, the more we will eat," Levitsky said. "If people did nothing other than eliminate snacks, their total calorie intake will go down."
A 500-calorie smoothie, for example, will defeat the strategy's purpose. "If you want to eat small frequent meals, take a look at your calories and really divide them up. If you're on 1,500-calorie diet, are you really having five 300-calorie mini-meals?" McKittrick asked.
An "all or nothing person" may be better off with three meals per day if a small snack quickly turns into a bigger one, as in the case of nuts. "Nuts are super healthy, but some people can't stop once they start eating nuts, and that can be a problem," McKittrick said.
The environment plays a role, too. If your office has a kitchen full of free snacks, it's a lot easier to go in and grab something like chips or cookies instead of planning your own healthy meals and bringing them in. Working from home, with constant access to the kitchen, can present similar challenges.
And then there are others who just don't want to be bothered with making eating an all-day affair. "Some just want to eat and get it done with, so they don't do well with small snacks. ... They're really busy, and they just don't have the time to deal with it, and so those people may be better off with three meals per day."
The bottom line is that either style of eating can offer health and weight-loss benefits. But what matters most is what will work for you.
"Maybe, down the line, we'll be able to test people to determine which eating frequency is optimal, but in the meantime, it's probably best to go by how you feel," McKittrick said.