Sedentary Activity and Body Composition of Middle School Girls: The Trial of Activity for Adolescent Girls

This study describes the relationships between sedentary activity and body composition in 1, 458 sixth-grade girls from 36 middle school, across the United States. Multivariate associations between sedentary activity and body composition were examined with regression analyses using general linear mixed, models. Mean age, body mass index, and percentage of body fat, were 12.0 +/- 0.51, 21.1 kg/m(2) +/- 4.8, 28.5 +/- 8.9, respectively. Girls averaged 7.7 +/- 1.2 sedentary hours per day and about 13 hr (similar to 97% of the day) of both sedentary and light activities. Overweight girls were significantly more (13 min; p < .003) sedentary, especially after school (> 2 p.m.; p < .01), and less physically active (p < .0001) than normal weight girls. The study documents small but significant associations between sedentary activity and adiposity.