Less sleep makes you eat more, gain weight

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Restricted sleep makes you eat more
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Not getting enough sleep can cause you to eat more and gain weight, says a new study published in the Proceedings of the National Academy of Sciences.

The study, led by University of Colorado Boulder, found that volunteers who got only 5 hours of sleep per night through the workweek, gained about 2 pounds when they had unlimited access to food.

“These findings provide evidence that sleep plays a key role in energy metabolism. Importantly, they demonstrate physiological and behavioral mechanisms by which insufficient sleep may contribute to overweight and obesity,” write the researchers in the abstract for the study.

Missing a night or two of sleep won’t necessarily make you gain weight, but consistently doing so during the week can.

"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 actually need," said study author, Kenneth P. Wright, director of the Sleep and Chronobiology Laboratory at the University of Colorado Boulder.

Wright and colleagues conducting the study found that even though staying awake longer burns more calories, the extra calories consumed exceeded the extra calories burned.

To help fight the obesity epidemic, the study’s researchers recommend encouraging people to get the sleep they need, although they acknowledge that doing so may not be so simple.

"I don't think extra sleep by itself is going to lead to weight loss, but I think it could help" said Wright.

"If we can incorporate healthy sleep into weight-loss and weight-maintenance programs, our findings suggest that it may assist people to obtain a healthier weight," he suggested, but he also said more research is needed first.

The study conducted by Wright and colleagues involved 16 young, lean and healthy adult volunteers who lived in a "sleep suite" for approximately two weeks.

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The "sleep suite", located at the University of Colorado Hospital, provides the volunteers a quiet and peaceful setting for sleep. Nevertheless, it is a controlled environment where researchers decide when lights go on and off. The rooms are also sealed, allowing the researchers to measure the amount of oxygen each volunteer breathes in, as well as the amount of carbon dioxide they breathe out. This enables them to determine how much energy each volunteer is using.

All volunteers had the opportunity to sleep 9 hours a night, and they were given only enough food to maintain weight. They were then divided into 2 groups for 5 days: 1) group one had their sleep restricted to 5 hours; and 2) group two was allowed to continue sleeping 9 hours.

Both groups were also given additional food that allowed them to eat larger meals and help themselves to snacks in between meals, ranging from yogurt and fruit – to potato chips and ice cream.

The researchers then switched the groups over for the next 5 days.

What were the results?

In short, the researchers found that restricted sleep, followed by overeating, resulted in weight gain. Specifically, when the volunteers sleep was restricted to 5 hours a night, they burned an approximate average of 5 percent more calories than when they could sleep up to 9 hours a night, but they consumed 6 percent more calories.

Moreover, they ate smaller breakfasts when their sleep was restricted, but they also ate more snacks after the evening meal -- in fact, the evening snacks totaled more calories than any one meal they ate previously that day, including the evening meal.

While on a restricted sleep schedule, they not only gained nearly 2 pounds, but getting less sleep also caused a shift in their biological clocks that led to an "earlier circadian phase of wake time", the researchers said.

However, when changing from restricted sleep to sufficient sleep, the volunteers experienced a slight drop in weight due to a reduction in the number of calories they ate, especially those consisting of fats and carbohydrates.

The researchers suggest their findings contribute to the growing amount of evidence that eating too much at night may lead to weight gain. According to Wright, the study shows that when people don't get enough sleep, they eat at night, which is when their bodies are not equipped for taking in food.

Wright and colleagues are now planning another study that looks at what time people eat and the effect it has on weight.

SOURCE: Proceedings of the National Academy of Sciences (March 2013; DOI:10.1073/pnas.1216951110). Abstract, University of Boulder Colorado

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