Prospective associations between physical activity level and body composition in adolescence: 1993 Pelotas (Brazil) Birth Cohort

Background: Physical activity may influence both fat and lean body mass. This study investigated the association between physical activity in children between the ages of 11 and 13 years and both fat and lean mass. Methods: A subsample of the 1993 Pelotas (Brazil) Birth Cohort was visited in 2004.2005 and 2006.2007. Physical activity was estimated through standardized questionnaires. Body composition (ie, fat and lean mass) was measured using deuterium dilution. Those with moderate-to-vigorous activity greater than 420 min/wk were classified as active, and physical activity trajectory was defined as being above or below the cutoff at each visit. Results: Four hundred eighty-eight adolescents (51.8% boys) were evaluated. The mean difference in fat mass in boys and girls who reported ≥ 420 min/wk of physical activity in both visits compared with those who were consistently inactive was.4.8 kg (P ≤.001). There was an inverse association between physical activity and fat mass among boys in both crude and confounder-adjusted analyses, whereas for girls, the association was evident only in the crude analysis. There was no significant association between physical activity and lean mass. Conclusion: Physical activity may contribute to tackling the growing epidemic of adolescent obesity in low- and middle-income countries.