It used to be that someone who wanted to lose weight was advised to stick to three square meals a day. For adults, at least, snacking was considered an unnecessary source of extra calories, and if you were hungry between meals, well, tough; you'd just have to wait for the next one. Nowadays, it's a rare diet plan that doesn't include planned snacks. Without a little something at 4 p.m., many diet books say, you're going to get hungry and blow your diet when dinnertime arrives.
So which is it? If you're trying to lose or maintain weight, should you snack or not? And if you should, how and what should you eat?
First, let's get one thing straight: Snacking appears to be neither significantly better nor worse for you, biologically speaking, than not eating between meals. In animals, at least, studies suggest that indicators of health actually improve when rodents fast intermittently—that is, alternating days of eating to their hearts' desire and eating nothing. In humans, one study published in 2007 had subjects eat either three meals a day or the same number of calories restricted to a four-hour window in the early evening. There were no major differences in health indicators like blood pressure, says Mark Mattson, lead author of the study and a neuroscientist at the National Institute on Aging. (The one-meal-a-day group actually had worse results for a few measures, like glucose tolerance, but Mattson chalks that up to study design issues, such as the timing of blood draws.)
Margriet Westerterp, a professor of human energetics at Maastricht University in the Netherlands, says that while eating more meals per day may have a favorable impact on blood glucose and insulin levels, the effect isn't strong enough to promote weight control.
Physiological studies in the lab are one thing. Free-ranging human behavior is another, especially when those humans are tempted by abundant food almost everywhere they go. Under real-world conditions, "the longer we go without eating, the greater the risk of overeating," says Linda Spangle, a weight loss coach and author of 100 Days of Weight Loss. "We get hungry. We get tired. We lose our common sense." While everyone is different and some people are fine with three squares, she says in her experience most people are better off eating more often, like every three to four hours. Dietitian Amy Jamieson-Petonic, a spokesperson for the American Dietetic Association and director of wellness coaching at the Cleveland Clinic, says snacks lower the chances dieters will feel deprived.
Here's the catch: Those snacks have to be appropriately sized. "You have to watch out for when snacks become meals," says Melanie Douglass, a dietitian and personal trainer based in Salt Lake City. A lot of people make that mistake, says Barry Popkin, director of the University of North Carolina's Inter-Disciplinary Obesity Center and author of The World Is Fat. We are eating more between regular meals, to the point that those in-between calories may make up nearly 30 percent of daily calories, depending on age and gender, he says. Plus, the snacks we're eating tend to be more calorie-dense than a regular meal. People don't wait to eat until they're hungry; they just eat all the time—in the car, in the classroom, at their desk at work. "The reality is that people are not eating seven 200-calorie meals a day," says Popkin. "They're having normal meals and then large snacks." That's what you want to avoid.
An appropriate snack in a typical 2,000-calorie-a-day diet is about 150 to 200 calories, says Douglass. (That assumes three main meals at 500 calories each, plus two or three snacks during the day.) And that's not a whole lot—a piece of string cheese and a piece of fruit, for example. She advises you start with fruits and vegetables, and while it's great to have both protein and carbs at once, don't get too obsessed with that idea. "It's OK to have an apple in the morning and nuts in the afternoon," she says.