Research subjects who slept only four hours a night for two nights had an 18 percent decrease in leptin, a hormone that tells the brain there is no need for more food, and a 28 percent increase in ghrelin, a hormone that triggers hunger.
The study volunteers, all healthy young men, reported a 24 percent increase in appetite, with a surge in desire for sweets, such as candy and cookies, salty foods such as chips and nuts, and starchy foods such as bread and pasta.
"This is the first study to show that sleep is a major regulator of these two hormones and to correlate the extent of the hormonal changes with the magnitude of the hunger change," said Eve Van Cauter, Ph.D., professor of medicine at the University of Chicago. "It provides biochemical evidence connecting the trend toward chronic sleep curtailment to obesity and its consequences, including metabolic syndrome and diabetes."
In the last 40 years, American adults have cut their average sleep time by nearly two hours. In 1960, U.S. adults slept an average of 8.5 hours a night. By 2002, that had fallen to less than seven hours a night. Over the same period, the proportion of young adults sleeping less than seven hours increased from 15.6 percent to 37.1 percent. Now, only 23.5 percent, or less than one out of four young adults, sleeps at least eight hours a night.
As sleep time fell, average weights rose. In 1960 only one out of four adults was overweight and about one out of nine was considered obese, with a body mass index of 30 or more. Now two out of three adults is o
Contact: John Easton
University of Chicago Medical Center