4. Trimmer Waist
If you sleep enough you can lose weight. Plenty of research confirms that adults who sleep less than six hours a night are at higher risk of being overweight. (Among children, sleeping less than 10 hours can cause unhealthy weight gain.)
According to a recent study at the University of Colorado, the effect of sleep may be even more powerful than we realized. The new study indicates that even just a few sleepless nights in a row can cause almost instant weight gain. Participants gained on average two pounds after one week of five-hour nights. Granted the study was small—16 men and women were tracked for two weeks—but it may have real-world implications.
One reason for this weight gain is because a lack of sleep increases hunger and appetite. Researchers have found a biochemical reason for this: Insufficient sleep can decrease levels of leptin—a hormone that tells us when we’ve eaten enough and suppresses appetite—and it also increases ghrelin, a hormone that signals the body to eat by stimulating hunger.
Not only does lack of sleep trigger appetite, it also increases the craving for high-fat, high-carbohydrate foods—aka junk foods. Researchers at Harvard University, for example, found that if you’ve missed even just an hour or two of sleep, you’re more likely to give in to junk food the next day. Other researchers concur, and some brain-imaging studies have even depicted sleep deprivation activating the “junk-food pleasure centers” of the brain.
And there are even more weighty reasons for giving your tired body more sleep: In a small study in the Annals of Internal Medicine, researchers found that when dieters slept 5½ hours a night for two weeks, they burned less fat and more muscle than those who slept 8½ hours. A Swedish study published in Sleep Medicine showed that in women under age 50, sleeping less than five hours or more than 10 hours per night was associated with a larger weight size and abdominal fat. Cortisol secretion (the stress hormone linked to belly-fat accumulation) is at its lowest at night, but sleep loss boosts cortisol the day after a night of poor sleep.
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