Sleep tight, stay slim. Is it that simple?

Parents have another good reason to make sure their child gets a good night's sleep: Recent research suggests that children who do not get enough sleep may be at higher risk of becoming overweight than those who watch too much television or never exercise.

According to a study by Angelo Tremblay, PhD, of Laval University in Quebec, Canada, school-age children who got the least amount of sleep were three times more likely than those who got a full night's rest to be overweight or obese. Other factors examined in the study, including parental obesity, physical activity, and time spent watching television, were less likely to result in a higher risk of overweight and obesity than was time spent sleeping, reported Dr. Tremblay in the March 2006 issue of the International Journal of Obesity.

To conduct the study, researchers measured the body weight, height, and waist circumference of 422 children-divided equally between boys and girls-between 5 and 10 years of age. Time spent sleeping and lifestyle and demographic factors were collected from telephone interviews with parents. Twenty percent of boys and 24% of girls were determined to be overweight or obese.

Children who slept 10 or 11 hours a day were significantly more likely to be overweight or obese than those who slept 12 or 13 hours a day. Those who slept just eight to 10 hours a day were even more likely to be overweight or obese.

Children whose parents are obese were slightly more than twice as likely to be obese or overweight than those whose parents were not, and children who watched more than three hours of television daily were twice as likely to be obese or overweight than those who watched television for less time. Last, children who never exercised were 45% more likely to be overweight or obese.

According to the "Guide to Your Child's Sleep," published by the American Academy of Pediatrics, exactly how much sleep a school-age child needs depends on his (her) age and level of activity.