Sleeping only five hours a nightand snacking more can make you add nearly a kilo in just a week, a new study has found.
Sleeping just five hours a night over a week and having unlimited access to food caused participants in a new study led by the University of Colorado Boulder to gain nearly a kilogramme of weight.
The study, performed in collaboration with the CU Anschutz Medical Campus, suggests that sufficient sleep could help battle the obesity epidemic.
"I don't think extra sleep by itself is going to lead to weight loss. Problems with weight gain and obesity are much more complex than that," said Kenneth Wright, director of CU-Boulder's Sleep and Chronobiology Laboratory, which led the study.
"But I think it could help. If we can incorporate healthy sleep into weight-loss and weight-maintenance programmes, our findings suggest that it may assist people to obtain a healthier weight. But further research is needed to test that hypothesis," Wright added.
In the new study, published in the Proceedings of the National Academy of Sciences, the researchers found that, while staying awake longer requires more energy, the amount of food study participants ate more than offset the extra calories burned.
"Just getting less sleep, by itself, is not going to lead to weight gain. But when people get insufficient sleep, it leads them to eat more than they actually need," Wright said in a statement.
For the study, researchers monitored 16 young, lean, healthy adults who lived for about two weeks at the University of Colorado Hospital.
The study found that on average, the participants who slept for up to five hours a night burned 5 per cent more energy than those who slept up to nine hours a night, but they consumed 6 per cent more calories.
Those getting less sleep also tended to eat smaller breakfasts but binge on after-dinner snacks. In fact, the total amount of calories consumed in evening snacks was larger than the calories that made up any individual meal.
"When people are sleep-restricted, our findings show they eat during their biological nighttime when internal physiology is not designed to be taking in food," said Wright.
Wright and his colleagues also found that men and women responded differently to having access to unrestricted food.
Men gained some weight even with adequate sleep when they could eat as much as they wanted, while women simply maintained their weight when they had adequate sleep, regardless of how much food was available.
Both men and women gained weight when they were only allowed to sleep for up to five hours.