Battling Fat? Get More Sleep

Studies link a shortage of shut-eye with obesity and diabetes.

Woman sleeping in bed
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[Read: The Trouble With Sleep Texting.]

If you assume you're safe because study conditions tend to be fairly extreme, think again. People who regularly get less than the optimum amount of sleep have been observed to eat 200 to 500 more calories per day than people who do not. "You prefer different foods, more of them, and at the wrong time of day," Buxton says. "Nobody is eating a salad in the middle of the night."

He recommends that people minimize TV and computer time in the two hours before bed, or at least dim the screen. That cold blue color "is the most circadian-disrupting," he says. He also suggests downloading the free app f.lux, which warms up the hue of the display at night.

If it comes to a tough choice, should you skimp on sleep to squeeze in a workout? No. When you drop below 6 ½ or six hours of sleep, says Ojile, "you need sleep more than you need to exercise."

[Read: Trouble Sleeping? Ask Yourself Why.]