According to a study presented at the American Thoracic Society Conference recently, women who sleep five hours or less a night weigh more than those who sleep 7 hours or more. The 16 year study found that women who slept for 5 hours a night were 32% more likely to exhibit significant weight gain and 15% more likely to become obese over the course of the study, as compared with women who slept for 7 hours.

The study consisted of around 68,000 middle-aged women. They were asked to monitor the amount of time they spent sleeping and to report their weight every two years for the duration of the study.

On average, women who slept for 5 hours or less per night weighed 5.4 pounds more, at the beginning of the study, and gained an additional 1.6 pounds over the following 10 years, than those sleeping for 7 hours.

The researchers looked at the women’s diets and exercise patterns to see if this could account in part of the findings. There appeared to be no difference in exercise patterns, such as running, jogging or playing tennis, between the various sleep groups.

Previous studies have shown, however, that after only a few days of sleep restriction hormones increase stimulation of the appetite, one possible cause for the additional weight gain.