Too little sleep with unlimited food availability leads to too much eating and weight gain, according to a small new study.
"I don't think extra sleep by itself is going to lead to weight loss," Kenneth Wright, director of the Sleep and Chronobiology Laboratory at the University of Colorado, Boulder, said in a university news release. "Problems with weight gain and obesity are much more complex than that. But I think it could help."
Wright and colleagues monitored 16 young, lean, healthy male and female adults who lived for about two weeks at the University of Colorado Hospital, which has a sleep suite. For the first three days, all the participants had the opportunity to sleep nine hours a night and were given meals that contained only enough calories to maintain their weight.
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For the next five-day period, the participants were split into two groups. One group's sleep was limited to five hours a night, while the other group could sleep for nine hours. Both groups were offered larger meals and had access to healthy and unhealthy snacks throughout the day. After those five days, the groups switched.
On average, participants whose sleep was limited to five hours burned 5 percent more energy than those who could sleep for nine hours, but they consumed 6 percent more calories.
Participants who got less sleep also tended to eat smaller breakfasts but binged on after-dinner snacks. The total number of calories they consumed in evening snacks was larger than the calories in any single meal, according to the study, which is scheduled for March publication in the journal Proceedings of the National Academy of Sciences.
That finding adds to growing evidence that overeating at night may contribute to weight gain, the researchers said.
Men and women responded differently to having as much food as they wanted, the study found. Men gained some weight even with sufficient sleep, while women maintained their weight. Both men and women gained weight when their sleep was limited to five hours.