Although it might seem intuitive that under-sleeping leads to overeating, science hasn’t yet found a direct cause-and-effect relationship between lack of sleep and being overweight. “There is a very, very strong link,” says Jim Hill, director of the Colorado Nutrition Obesity Research Center at the University of Colorado and a spokesman for the American Society for Nutrition. “People with sleep problems tend to have obesity. Why? That’s where the research is.”
In one of the latest studies, Marie-Pierre St-Onge of the New York Obesity Nutrition Research Center at St. Luke’s-Roosevelt Hospital found that sleep-deprived people tend to burn the same number of calories — in her study, about 2,600 per day — as people who enjoy a full night’s sleep. But her research, published in the August issue of the American Journal of Clinical Nutrition, found that sleep-deprived subjects consumed about 300 more calories per day (2,800 vs. 2,500) than the well-rested subjects. Because it takes just 3,500 calories to add a pound to your body, St-Onge says, “if people kept that up for a while, it would add up really, really quickly.”
Still to be determined: Do sleep deficits actually cause people to become overweight? Or does being overweight cause people to not get enough sleep? Or might the two conditions share some underlying factor that’s not been found?
Michael Breus knows those questions need answers. But he’s not waiting for all the dots to be connected. Breus, a prominent sleep disorders specialist, has recently published “The Sleep Doctor’s Diet Plan: Lose Weight Through Better Sleep” (Rodale/Mindworks, 2011). As the subtitle suggests, he’s convinced that the body responds to too-short sleep by packing on pounds — and, conversely, getting more sleep is an effective weight-loss strategy. (Although the book touts Breus as the Sleep Doctor, he is a psychologist with a PhD, not a physician.)
Breus spells out (and supports by citing research) several means by which too little sleep could lead to weight gain. When you’re sleep-deprived, he says, your body moves into a different mode. “On a physical level, the key things are hormones,” Breus says. When you lack sleep, he explains, “your metabolism slows down. Your body is trying to conserve energy stores” to carry you through the longer period of wakefulness. That slowdown triggers the release of cortisol, a hormone that your body secretes in response to stress and that boosts your appetite: Your body senses it needs more energy, so it demands more food.
At the same time, Breus says, sleep deprivation causes your body to release more ghrelin, the hormone that signals hunger, and less leptin, the hormone that tells your body it’s full. When those hormones are out of whack, your body wants more food and lacks the sensitivity to know when to stop eating. Combined with the fact that you’re awake for more hours a day, that hormone cocktail can send you snacking into the wee hours.