Getty ImagesBy Matt McMillen
Sleep deprivation can leave you feeling drowsy and slow-witted, but that's not all: New research suggests it may also rev up your appetite.
After sleeping for only four hours, people tend to eat more calories on the following day than when they get a good night's sleep, the study found. This was especially true of women, who consumed an average of 329 more calories when sleep deprived than when well rested. By contrast, men consumed just 263 more.
These findings may explain the link between insufficient sleep and overweight that has been shown in previous studies, says the lead researcher, Marie-Pierre St. Onge, Ph.D., a research associate at Columbia University's New York Obesity Research Center. "This study shows a possible causative effect," she says.
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Overweight people often have sleep problems-most notably sleep apnea, a breathing disorder that causes frequent awakenings-but it's not clear if they're overweight because of their sleep problems, or if their sleep problems result from being overweight.
St. Onge's study may be a step toward answering that "chicken-or-the-egg question" because it included only people of normal weight and therefore eliminated the influence of existing overweight or obesity, says Gina Lundberg, M.D., a clinical assistant professor of cardiology at the Emory University School of Medicine, in Atlanta.
However, Lundberg cautions that the study's small size makes it impossible to draw any firm conclusions. (She was not involved in the research.)
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The study, which was presented today at an American Heart Association conference in Atlanta, included 13 male and 13 female volunteers between the ages of 30 and 45, all of whom were healthy sleepers of normal weight. Each of the participants spent two six-day stints under close supervision in a sleep lab. During the first stint they could sleep up to nine hours per night, and during the other they were restricted to just four hours. They were not allowed to leave the lab, nor were they allowed to nap.
For the first four days of the study, they all ate a fixed diet of cereal and milk in the morning and frozen entrées for lunch and dinner. Then, on the last two days of the study, they could choose what they ate. They were given an allowance and taken shopping, the only restriction being that they had to buy food with clearly marked nutritional content so the researchers could properly measure it.
In addition to consuming more calories, the volunteers seemed to gravitate to high-fat, high-protein foods when sleep deprived. "Ice cream was a favorite," St. Onge says.
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Both men and women ate more protein-rich foods on short sleep, but only women ate more fat. While men ate the same amount of fat no matter how much sleep they got, the women averaged 31 more grams of fat after sleeping for four hours.
The sleep-deprived participants may simply have been looking for a quick source of energy to perk themselves up, St. Onge says, but it could also be that lack of sleep impairs the ability to make healthy food choices.
"It has an impact on cognitive restraint," she says. "High-fat food is tempting, and maybe on short sleep you can't restrain yourself as well, while on full sleep you can resist more easily."
The lack of restraint displayed by the sleep-deprived volunteers could have unhealthy consequences over the long term, Lundberg says. Regularly eating an extra 300 calories a day would add up to about 30 pounds of weight gain over the course of a year, increasing the risk of heart disease, diabetes, and other chronic illnesses associated with overweight and obesity, she says.
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The study offers "one more data point that sleep-deprived people have more weight issues," Lundberg adds. "And if we understand the problem better, we'll be better able to fix the problem."
St. Onge's study was presented at the American Heart Association's annual conference on nutrition, physical activity, and metabolism. Unlike the studies published in medical journals, the research presented at the meeting has not been thoroughly vetted by other experts in the field.
Getty ImagesBy Matt McMillen