Influence of physical activity on change in weight status as children become adolescents

Physical activity (PA) has been shown to have a positive effect on weight status, but habitual physical activity declines as youth age, yet some adolescents do not gain weight. PURPOSE: To determine if changes in weight status over 5 years during adolescence are associated with changes in PA levels. PROCEDURES: A longitudinal study of 377 girls and 388 boys tested initially at ages 9-11 years old and 5 years later (age 14-16 years old). The sample was grouped by initial and final weight status: N-N = youth with BMIs < 85(th) percentile at both points (n = 456; 60%); O-O = overweight youth with BMIs > or = 85(th) percentile at both time points (n = 186; 24%); O-N = overweight youth whose BMI declined to < 85(th) percentile (n = 66; 9%); N-O = normal weight youth who became overweight (n = 57; 7%). Stature and body mass were measured and habitual PA levels were obtained during the survey. RESULTS: Total PA scores, moderate (MPA) and vigorous activity (VPA) declined by 65-70% for all groups (p = 0.002). Girls in the O-N groups had less of a decline in PA than the girls in the N-O group (p < 0.05). No differences were evident for the boys. These results were consistent even when adjusted for developmental stage or race/ethnicity. DISCUSSION: Overweight children as young as 9 years old are already participating in less PA than normal weight youth. Although PA declined from childhood to adolescence, overweight girls with normalized weight status, had less of a decline in MPA or VPA than normal weight girls who became overweight. The data highlight the complexity of the interrelationship between physical activity and weight gain or loss. These data suggest that habitual physical activity levels, especially in girls, may have a role in adolescents attaining a healthy weight status.