Slumber Longer to Get Slimmer: Study Links Sleep Time to Weight Loss

(Oct. 5) -- Logging adequate sleep might be a key component of losing unneeded fat, rather than valuable lean body mass.

A small study on 10 overweight or obese adults, published in this week's Annals of Internal Medicine, suggests that diet and exercise are only part of the solution in attaining a healthy body mass and composition.

Study participants were sequestered to a controlled environment for four weeks, with their meals, exercise routines and sleep schedules strictly monitored. Because self-reporting is often skewed, the approach makes the research all the more intriguing.

Longer slumberers get slimmer

In one phase of the study, participants were given 8.5 hours for sleeping each night. In the other, they received a mere 5.5 hours allotted to nightly slumber. For the duration of the research, all participants were consuming a calorie-controlled diet.

While weight loss held steady, at around 6.6 pounds during each 14-day phase, researchers found a major difference in how much fat and muscle participants lost.

More sleep meant more fat loss (3.1 pounds), while less sleep yielded only 1.3 lost pounds of body fat. The rest of the mass lost was lean body mass.

"The loss of lean body mass is an unwanted side effect of all weight loss diets. This side effect was increased by sleep reduction in our study," Dr. Plamen Penev, one of the study's authors, told ABC News.

What accounts for the nocturnal net loss?

Fat loss is associated with better health outcomes. Losing muscle, on the other hand, slows down metabolism and makes it harder to lose weight and keep it off.

Insufficient sleep is thought to affect key hunger hormones, and might also trigger changes in where and how the body chooses to obtain energy.

Previous research has already found that sleep deprivation spurs hunger, probably because of increased levels of a hormone called ghrelin. Which means that the detrimental effects of insufficient sleep might be underestimated by this study, where diets were controlled.

The bottom line: Dieters need a good night's rest

"The bottom line is that if people are trying to diet and lose weight for health reasons, it makes sense to get a sufficient amount of sleep," Penev told The New York Times. "If they're not getting enough sleep as they diet, they may have higher levels of hunger and be struggling to adhere to the regimen."

Further study, including long-term real-world evaluations and larger participant pools, will help researchers nail down the exact link between sleep and body composition.

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