The prevalence of obesity in children in the United States has increased over the past few years. A number of studies have revealed that obese children are at increased risk for developing dyslipidemia, hypertension, diabetes mellitus and other weight-related morbidities. This increase in childhood obesity is multifactorial. Despite the fact that the caloric intake in children in the United States has not increased substantially over the past few years, the prevalence of obesity continues to rise. This increase in the number of obese children may be a result of reduced physical activity. Crespo and associates examined the association between physical activity, television viewing time and energy intake using a nationally representative sample of U.S. children ages eight through 16 years.

The study was a cross-sectional survey consisting of a home interview and a detailed clinical examination. A total of 4,069 children participated in the study. Included in the interview were questions about the daily number of hours of television viewing, weekly participation in physical activity and diet. A portion of the clinical examination included measuring the participant's height and weight. Each participant's body mass index (BMI) was calculated using that data.

The prevalence of obesity in the study population was lowest among children who viewed television for one hour or less per day and highest among those who viewed television for four or more hours per day (see accompanying figure). Girls exercised less than boys and consumed fewer kilojoules per day. Non-Hispanic white boys were more likely to participate in physical activity five or more times per week than any other race/ethnic or sex group. After controlling for other variables, television viewing was positively associated with obesity in girls in this study.

The authors conclude that the higher the television viewing time per day, the higher the association with obesity in children. To reduce the trend of increasing prevalence of obesity in children, physicians need to assist children and parents in limiting the amount of sedentary activity and promoting a more active lifestyle. Activity will improve the balance of energy intake and expenditure in children and lead to a reduction in the prevalence of obesity.