The recommended seven to eight hours of sleep can be hard to get. But here's a good excuse to make sure you catch those extra zzz's: a study shows that healthy adults who don't get enough sleep gained significantly more weight than did their well-rested counterparts. The research features 225 non-obese subjects in a controlled lab setting. Some were on a restricted sleep schedule, in bed only between the hours of 4 a.m. and 8 a.m. Others had from 10 p.m. to 8 a.m. to lounge in bed. After just five days, those sleeping only four hours a night had gained, on average, more than two pounds, compared to less than a quarter-pound gained by the rested group. Men gained more than women did. The findings are in the journal Sleep. Why the weighty consequences? Sleep disruption has been linked to high levels of hormones that make people feel hungrier. And the new study found that people filled the extra time they were awake by filling their stomachs. So one step to slimming down might be to rest up.