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Dieting? Be sure you get enough Zzzzzs

If you’re trying to lose weight, make sure you’re not cutting down on your sleep along with those extra calories.

Not getting enough sleep makes it more difficult for overweight people to shed body fat, a new study has found. Sleep deprivation also boosts the body’s production of a hormone (ghrelin) that stimulates hunger.

That means you’re doubly sabotaging your diet if you’re not getting enough sleep. And, as the authors of this new study point out, sleep loss is a growing problem in the United States. A report published last year by the Centers for Disease Control and Prevention reported that 29 percent of American adults sleep less than 7 hours per night, and some 50 to 70 million have chronic sleep disorders that make it difficult for them to either fall asleep or stay asleep.

We are a nation of tired people.

For this new study, researchers recruited 10 (3 women, 7 men) overweight but otherwise healthy volunteers, aged 35 to 49, to spend two 14-day sessions in a laboratory at the University of Chicago’s General Clinical Resource Center. The volunteers had their calories restricted to 90 percent of what each of them needed to maintain their weight without exercising.

For one session, the volunteers were permitted to sleep (or rest) for an 8.5-hour period each 24 hours. (They slept an average of 7 hours and 25 minutes.) For the other session, this sleeping period was cut back to 5.5 hours.

The volunteers lost an average of 6.6 pounds during each of the sessions. When they got enough sleep, they lost an average of 3.1 pounds of body fat and 3.3 pounds of fat-free body mass, mostly muscle (protein). But when their sleep was restricted, they lost an average of 1.3 pounds of body fat and 5.3 pounds of fat-free mass.

In addition, during the sleep-deprived period the volunteers’ levels of ghrelin increased by more than 12 percent. Not only does ghrelin stimulate hunger, it also promotes the retention of body fat.

The fact that the study’s volunteers were in an environment where their calorie intake was tightly controlled may have helped them lose weight even when their ghrelin levels were rising, said the study’s authors. In a “real life” situation, however, people may find it more difficult to resist those hunger pains.

This was a small study, and it followed people during a limited period of time. (These kinds of in-lab studies are very expensive to do.) But its findings are a strong indication that dieters should make a good night’s sleep a central feature of their weight-loss plan.

The study, which was funded by the National Institutes of Health, was published Monday in the Annals of Internal Medicine.

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