The Dream Diet: Losing Weight While You Sleep

Lose weight while you sleep. It sounds like something you'd hear on a late night infomercial -- just around the time you are reaching for that bag of cookies because, well, you can't sleep.

But as wild as the idea sounds, substantial medical evidence suggests some fascinating links between sleep and weight. Researchers say that how much you sleep and quite possibility the quality of your sleep may silently orchestrate a symphony of hormonal activity tied to your appetite.

"One of the more interesting ideas that has been smoldering and is now gaining momentum is the appreciation of the fact that sleep and sleep disruption do remarkable things to the body -- including possibly influencing our weight," says David Rapoport, MD, associate professor and director of the Sleep Medicine Program at the New York University School of Medicine in New York City.

While doctors have long known that many hormones are affected by sleep, Rapoport says it wasn't until recently that appetite entered the picture. What brought it into focus, he says, was research on the hormones leptin and ghrelin. First, doctors say that both can influence our appetite. And studies show that production of both may be influenced by how much or how little we sleep.

In fact, have you ever experienced a sleepless night followed by a day when no matter what you ate you never felt full or satisfied? If so, then you have experienced the workings of leptin and ghrelin.

How Hormones Affect Your Sleep

Leptin and ghrelin work in a kind of "checks and balances" system to control feelings of hunger and fullness, explains Michael Breus, PhD, a faculty member of the Atlanta School of Sleep Medicine and director of The Sleep Disorders Centers of Southeastern Lung Care in Atlanta. Ghrelin, which is produced in the gastrointestinal tract, stimulates appetite, while leptin, produced in fat cells, sends a signal to the brain when you are full.

So what's the connection to sleep? "When you don't get enough sleep, it drives leptin levels down, which means you don't feel as satisfied after you eat. Lack of sleep also causes ghrelin levels to rise, which means your appetite is stimulated, so you want more food," Breus tells WebMD.

The two combined, he says, can set the stage for overeating, which in turn may lead to weight gain.

Studies: Those Who Sleep Less Often Weigh More

How the hormones leptin and ghrelin set the stage for overeating was recently explored in two studies conducted at the University of Chicago in Illinois and at Stanford University in California.

In the Chicago study, doctors measured levels of leptin and ghrelin in 12 healthy men. They also noted their hunger and appetite levels. Soon after, the men were subjected to two days of sleep deprivation followed by two days of extended sleep. During this time doctors continued to monitor hormone levels, appetite, and activity.