If you're looking for a better way to control your weight, one study suggests that getting a good night's sleep might be a good place to start.
Study author Eve Van Cauter, a professor of medicine at the University of Chicago, and her colleagues measured the circulating levels of the hormones leptin and ghrelin in 12 healthy men in their 20s.
Leptin tells the brain when it doesn't need more food and ghrelin triggers hunger.
Then they measured the levels after two nights of 4 hours in bed, with an average sleep time of 3 hours, 53 minutes; and again after two nights of 10 hours in bed, with an average sleep time of 9 hours, 8 minutes.
Then the researchers asked the men to complete questionnaires about their hunger and the desire for different types of food.
When the participants in the study slept less than 4 hours nightly, leptin levels decreased by 18% and ghrelin levels increased 28%.
In addition, their reported hunger increased by 24%, and they craved calorie-packed foods with high carbohydrate content, such as candy, cookies and cake, the researchers report.
Lack of sleep changes the circulating levels of these hormones, boosting appetite and a preference for high-calorie, high-carbohydrate foods, the researchers report.
Echoing previous research that has found a link between lack of sleep and the risk of weight gain, this study is believed to be the first to show that sleep is a major regulator of leptin and ghrelin.
"That is the major finding that we identified the mechanism by which sleep loss affects appetite. The changes in hunger are proportional to the changes in the hormones," says Van Cauter.
Another expert who has studied the effect of sleep loss on weight says this study adds to the growing body of research on the subject. "This, to my knowledge, is the first real experimental study of sleep deprivation on food intake and regulatory hormones," says Dr. Steven Heymsfield, a professor of surgery at Columbia University and St. Luke's-Roosevelt Hospital Center in New York City.
While the study looked at a small number of participants and was not lengthy, it was "very well-designed and controlled," Heymsfield notes.
In another study, Heymsfield discovered that people who slept 4 hours or less a night were 73% more likely to be obese than those who slept 7 to 9 hours nightly.
Why sleep deprivation affects the levels of hormones that regulate hunger is unknown, Van Cauter says.
Some studies have suggested that sleep loss is tied to an increase in sympathetic nervous system activity, which can inhibit the release of leptin, the hormone that tells a person to stop eating
Van Cauter says she would like to investigate whether the amount of sleep someone gets affects how well he/she adheres to a diet.
She also wants to study whether some people might be immune to sleep loss and an increase in appetite.
"Know how much sleep you need, know when you are running a sleep debt, and pay it," Van Cauter advises.
Heymsfield adds, "If you have a weight problem to begin with, watch out for periods of sleep deprivation. You will be vulnerable to weight gain."
Facts to Sleep On
Sleep deprivation is a fact of life for many Americans.
Sleep duration among young adults, ages 20 to 24, in the United States has decreased by approximately 2 hours per night since the 1960s, according to the National Sleep Foundation. In 2002, more than 37% of young adults said they slept less than 7 hours a night, compared with approximately 16% in 1960.