Harvard Health Letter

Sleep helps with fat reduction

Losing the excess fat a lot of us carry around is never easy, and a small study shows that not getting enough sleep may make it even harder.

Researchers at the University of Chicago put 10 moderately overweight people (average BMI, 27.4) on pretty strict diets (about 1,450 calories a day). For two weeks, six were allowed to sleep 8 hours a night while the other four were restricted to sleeping just 5 hours. Several months later, for a separate two-week study period, people who had been allowed to sleep for 8 hours had their sleep restricted to 5 hours, while the short sleepers were allowed to get a full night's rest this time.

At the end of each of the two study periods, the amount of weight loss (about seven pounds) was the same regardless of the amount of sleep. But when people were allowed to get a full night's rest, more than half of the weight lost was fat, while on short sleep, only a quarter of it was. People also lost more muscle and were hungrier when their sleep was curtailed.

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