Associations between accelerometer-measured physical activity and body fatness in school-aged children

Background: The main aim of the study was to examine the cross-sectional associations between objectively measured physical activity (PA) and body fatness in 7-12-year-old children. Methods: We performed an analysis of 365 children (209 girls). Participant recruitment was performed in eight randomly selected elementary schools in cities and towns with various numbers of inhabitants. The body composition analysis was performed according to a multi-frequency bioelectrical impedance analysis; PA was monitored using an accelerometer. Results: In terms of the overall PA, boys were more active than girls. No significant associations (unadjusted and adjusted models) were found between light PA and all body fatness indicators in either sex. Moderate-to-vigorous PA was significantly negatively associated with all body fatness indicators only in girls. These associations strengthened after adjustment for age, height and sedentary time (beta ranging from -0.49 to -0.36, P <= 0.01). In contrast, vigorous PA was strongly negatively associated with body fatness indicators only in boys. In the fully adjusted model the significant negative associations were found for fat mass percentage (beta = -0.15, P = 0.048) and fat mass index (beta = -0.15, P = 0.040). Conclusions: The present study suggests that increasing sex-specific PA of different intensities may be an appropriate approach for decreasing body fatness in children. Longitudinal studies are needed to verify these associations.