Researchers from the Seattle Children's Research Institute have found that teenagers who sleep less are more likely to gain weight. Their study, they say, is one of the first studies to document an association between sleep duration and weight in adolescents, even after controlling for calorie intake, activity level and depressive symptoms.

"Sleep has long been recognized as an important health behavior," said lead author Leslie A. Lytle. "We are just beginning to recognize its relationship to overweight and obesity in children and adults alike."

Investigators collected data on 723 adolescents (mean age 14.7 years) about how long they slept on weeknights and weekends, and how frequently they experienced sleep problems. On three separate occasions, researchers also asked the youths about the foods and beverages they had consumed the prior day to determine how many calories they consumed.

To measure activity, participants wore accelerometers on their belts for seven days. Unlike pedometers, which count the number steps walked, these highly specialized devices measure movement on three different planes. In addition, the wearer cannot see any data on how active they are.

Researchers also measured participants' weight, body mass index (BMI) and percentage of body fat.

Results showed that shorter sleep duration was related to higher BMI. The relationship was especially strong for boys and for middle school students compared to those in high school. In girls, only less sleep on weekends was related to higher BMI.

Citation: Leslie A. Lytle, Keryn Pasch, Kian Farbaksh, 'Is Sleep Related to Obesity in Young Adolescents?', PAS Annual Meeting, May 2010