Good night’s sleep seems to be the third key to weight control along with cutting calories and getting exercise, according to the latest researches. The studies found that sleep-deprived volunteers had higher levels of the appetite-stimulating hormone and lower levels of the hormone that gives you the feeling of satiety.

“We strongly recommend that any weight-reduction program include getting enough sleep as one of their tips,” said University of Chicago sleep specialist Dr. Esra Tasali, co-author of one of the new studies.

The results of the study, conducted by Stanford University and University of Wisconsin researchers, were similar regardless of participants’ gender, eating and exercise habits or body mass index. Researchers determined the optimal amount of sleep for weight control to be 7.7 hours. But, if cutting back on sleep gives people more time to overeat, sleeping for too long leaves them less time for exercising.

According to the U. of C. researchers, during the past 50 years, the amount of time Americans sleep each night has decreased by one to two hours.

“During the same time period, the incidence of obesity has nearly doubled,” researchers wrote. “Additional studies should examine the possible role of chronic sleep curtailment as a previously unrecognized risk factor for obesity.”