Abstract

We analysed the relationship between formal and informal physical activity (PA) and the body mass index (BMI) in children. The participants of this study were 1369 boys (14±3 y) and 1297 girls (13±3 y), with ages between 10 and 19 years old. Data was collected by the application of a questionnaire about formal and informal PA. Weight and height were self-reported by the subjects and used to calculate the BMI. For data analyses t test, to independents samples, and X² were used. 64% of the boys and 49% of the girls reported participation in formal PA (X²(1)=67.217, p<0.001). Regarding the informal PA, 57% of the boys and 42% of the girls reported participation (X²(1)=61.338, p<0.001). The mean value of BMI for boys was 21 while girls were 20. Boys who reported participation in formal PA had a lower value of BMI than boys that did not (20.3 vs. 21.0: t(1136)=2.718, p=0.007), the same was verified for girls (19.7 vs. 20.3: t(1059)=3.376, p=0.001). On the other hand, significant differences between informal PA and BMI were not found in both genders. A relationship between formal PA and BMI was verified. However, the same did not happen to informal PA and BMI. These results suggests that formal PA must be encouraged for children, as it could be a strategy to fight pre-obesity and obesity.