Childhood obesity is a major health concern in the US. As of 2004, the National Health and Nutrition Examination Survey (NHANES) estimated that 17 per cent of children and adolescents are obese. Obesity is known to increase the possibility of cardiovascular risk factors, such as hypertension. Recent studies have shown that cardiovascular risk factors in childhood are significant predictors of preclinical atherosclerosis in adulthood.

Data was gathered regarding 546 subjects, aged 4 to 17 years, who were evaluated for obesity. Children and their parents were given a written questionnaire, which was used to estimate the average daily time spent watching TV, and then a physician verbally reviewed and confirmed the time estimate. The height and weight of the children were measured to determine a Body Mass Index (BMI) and their blood pressures were recorded.

Investigators determined that TV time was positively correlated with the severity of obesity. After controlling for race, site, and BMI score, both the severity of obesity and daily TV time were significant independent predictors of the presence of hypertension.

Writing in the article, Jeffrey B Schwimmer MD (Associate Professor of Pediatrics at University of California, San Diego and Director of Weight and Wellness at Rady Children’s Hospital – San Diego), states, "The current study illustrates the need for considerable physician and family involvement to decrease TV time among obese children.

"The American Academy of Pediatrics (AAP) recommends that children watch less than two hours of TV per day, but reports that only half (51 per cent) of pediatricians make this recommendation to patients…TV viewing is an attractive target for intervention, particularly among obese children with hypertension. Several studies have demonstrated that changing TV time alone can lead to weight loss, without any changes in physical activity."

In a commentary published in the same issue of the American Journal of Preventive Medicine, Stuart J H Biddle, from the School of Sport and Exercise Sciences, Loughborough University, UK, cautions that studies of TV viewing are part of a recent trend to study sedentary behaviors in general, and such studies are difficult to interpret.

He argues, "There is much debate concerning whether TV viewing is associated with obesity in young people. For example, an extensive meta-analysis of mainly cross-sectional studies showed that the relationship is very small…moreover, the small relationship may be a reflection of other trends.

"If obesity is causally related to TV viewing, as some suggest, how do we account for the following paradoxes: obesity levels are increasing but TV viewing figures are not, obesity increases during adolescence at the same time that TV viewing decreases, and boys watch more TV than girls but show less obesity and greater physical activity?

"Whatever the true findings, the association between sedentary behavior (TV viewing or other behaviors) and health outcomes, at least in youth, is likely to be complex and, as yet, unknown," he says.