There are new findings that not enough sleep may cause people to gain weight. Researchers say a lack of sleep can produce hormonal(激素的) changes that increase feelings of hunger. In one study, researchers in the United States examined information on more than 1000 people. The people had taken part in a long-term study of sleep disorders. Some people slept less than five hours a night. They had 15 percent higher blood levels of a hormone called ghrelin than people who slept eight hours. And they had 15 percent less of the hormone leptin. Experts say ghrelin helps make people feel hungry; leptin makes you feel full. The scientists say these hormonal changes may be a cause of obesity in Western societies. They note the combination that sleep limitation is common and food is widely available. The results were not affected by how much people exercised. People who are awake longer have more time to burn energy. But the researchers say loss of sleep may increase hunger especially for high-calorie foods, so people gain weight. It seems that, for survival, the body may be designed to store more fat during times with less sleep. Researchers from Stanford University in California and the University of Wisconsin did the study. They found that the best amount of sleep for weight control is 7.7 hours a night.  The Public Library of Science published the findings in its journal Medicine . Internet users can read the full study, free of charge, at plos. org.小题1:Not enough sleep can cause obesity by ______.
The more you sleep, the farther away you are from obesity. Those who don’t sleep at all are the most likely to put on weight. Sleeping contributes more to obesity than eating. It’s not wise to use sleep hours for exercise. 小题3:When you sleep 7.7 hours a night, you will ______ . have your ghrelin level rise and leptin level drop have your leptin level rise and ghrelin level drop have your ghretin and leptin levels properly balanced have your hunger increase and your weight decrease 小题4:The writer wrote this passage to _______ .
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