Scottsdale, Arizona - It might be. Recent studies have suggested an association between sleep duration and weight gain. Sleeping less than five hours - or more than nine hours - a night appears to increase the likelihood of weight gain.

In one study, recurrent sleep deprivation in men increased their preferences for high-calorie foods and their overall calorie intake. In another study, women who slept less than six hours a night or more than nine hours were more likely to gain 11 pounds (5 kilograms) compared with women who slept seven hours a night. Other studies have found similar patterns in children and adolescents.

One explanation might be that sleep duration affects hormones regulating hunger - ghrelin and leptin - and stimulates the appetite. Another contributing factor might be that lack of sleep leads to fatigue and results in less physical activity.

So now you have another reason to get a good night's sleep.