It should come as no surprise that overweight and obesity are linked to a less active lifestyle. A new report in the journal Pediatrics (Laurson, et al., 2008) quantifies the relative effects of physical activity (PA) and screen time (ST) -- time spent watching TV and playing video games -- on the likelihood that children will be overweight or obese.
The researchers monitored 709 children ranging from seven to twelve years old (318 boys and 391 girls) by having them wear pedometers for seven days, and reporting on their ST. This information was compared to guidelines previously endorsed by the American Academy of Pediatrics (AAP): no more than two hours of ST per day, and at least 11,000 and 13,000 steps per day for girls and boys respectively (PA).
On the basis of their reported activity, each child was then assigned to one of four categories: did not meet either PA or ST guidelines, met PA but not ST guidelines, met ST but not PA guidelines, and met both PA and ST guidelines.
Children -- both boys and girls -- who met both sets of guidelines had the lowest percentage of overweight and obesity, and those who met neither guideline were 4.5 times more likely (boys) and 3 times more likely (girls) to be overweight and obese. Approximately 36% of girls and 43% of boys fell into this least active category.
Since this was a cross-sectional study, i.e., it examined activity at just one time, it is not possible to tell if the combination of high ST and low PA was the cause or the result of the increased occurrence of overweight and obesity. It is possible that heavier children are less likely to be active, or more likely to favor sedentary activities. Further, since food intake was not measured, it is not possible to determine what differences might exist in that important determinant of body weight.
The authors pointed out that their study appeared to validate the utility of the AAP guidelines because a failure to meet guidelines was linked to an increased likelihood of overweight and obesity.
The take-home message is that the study supports encouraging children to limit ST and increase PA -- not a startling conclusion, but one that should be put into practice more widely if childhood obesity is to be diminished.