本篇阅读材料“为什么缺少睡眠会使人变胖？”选自《读者文摘》（原文标题：Why Lack of Sleep Could Be Making You Fatter ）。

　　Sleepless nights don’t just ruin your mood the next day—they could also damage your waistline. According to new research in the August issue of the American Journal of Clinical Nutrition, sleep deprivation can cause people to pack on extra pounds.
　　sleep deprivation 睡眠不足
　　pack on the pounds 长胖；变肥；增加体重
　　Researchers at the New York Obesity Nutrition Research Center at St. Luke’s-Roosevelt Hospital found that sleep-deprived people seem to burn the same number of calories as the well-rested, but they consume about 300 more calories a day. Given that it takes just 3,500 calories to add a pound to your body, those calories can quickly turn into extra weight.
　　well-rested 休息充分的
　　given that 只要是，考虑到；假定，已知
　　turn into 转变为；变成
　　But there are several other reasons that sleep loss could lead to weight gain, says sleep disorder specialist Michael Breus. When we get too little shut-eye, our metabolism slows down to conserve energy. That slowdown triggers the release of the hormone cortisol, which increases appetite. Your body thinks it needs more energy, so it asks for more food.
　　metabolism n. 新陈代谢
　　trigger v. 引发；引起
　　appetite n. 食欲；胃口
　　In a vicious cycle, sleep loss also causes our bodies to release more ghrelin, another hormone that signals hunger, and less leptin, the hormone that tells your stomach that it’s full. With your hormones off-kilter, your body wants more food and lacks the sensitivity to know when to stop eating. Not to mention that being awake more hours gives you more time to snack.
　　vicious cycle 恶性循环
　　not to mention 更不用说；更别提
　　"The later you’re up at night, the greater the likelihood that you’re going to eat,” Breus says. And “you’re more likely to eat high-fat, high-carb foods.”
　　likelihood n. 可能性；可能
　　One other contributing factor to such weight gain is that the body burns the most calories during REM sleep, a deeply restful phase. And less sleep means less time in REM.
　　For optimal health, experts say you should try to get 7.5 hours of sleep a night. If you have trouble sleeping, stick to a nightly routine, exercise during the day, banish worries to a journal, and keep pre-bedtime activities relaxing.
　　optimal adj. 最佳的；最理想的
　　stick to 坚持
　　banish v. 放逐；驱逐

　　Question time:
　　1. What's the influence of sleep deprivation according to the passage?
　　2. Why people sleep less gain weight according to the research?