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　　A study published Monday found that people who sleep less tend to be fat, and experts said it’s time to find out if more sleep will fight fatness．

　　“We’ve put so much emphasis on diet and exercise that we've failed to recognize the value of good sleep,” said Fred Turek, a physician at Northwestern University．

　　Monday’s study from Eastern Virginia Medical School in Norfolk covered 1,000 people and found that total sleep time decreased as body mass index - a measure of weight based on height - increased．

　　Men slept an average of 27 minutes less than women and overweight and fat patients slept less than patients with normal weights, it said．In general the fatter subjects slept about 1.8 hours a week less than those with normal weights．

　　“Americans experience insufficient sleep and fat bodies．Clinicians are aware of the burden of fatness on patients,” the study said．

　　“Our findings suggest that major extensions of sleep time may not be necessary, as an extra 20 minutes of sleep per night seems to be associated with a lower body mass index,” it added．

　　“We caution that this study does not establish a cause-and-effect relationship between restricted sleep and fatness(but)investigations indicating success in weight loss via extensions of sleep would help greatly to set up such a relationship．”

　　The study was published in the Archives of Internal Medicine along with an editorial by Turek and Northwestern colleague Joseph Bass commenting on it and related research．

　　In an interview, Turek said some studies have shown sleep causes declines in an appetite(胃口)suppressing protein hormone, and increases in another hormone that causes a longing for food．In addition neuropathies(神经疗法)in the brain governing sleep and fatness appear to overlap(重叠), he said．

　　Fatness has been rising dramatically in developed countries and reached epidemic(流行病)levels in the United States, it added, leading to a variety of health problems．