AGE-RELATED DECLINE IN PHYSICAL ACTIVITY IN OBESE AND NONOBESE CHILDREN189

This study investigated the age-related decline in physical activity in obese and nonobese children. The physical activity of 502 fourth-grade children (258 boys, 244 girls) in Southern California was examined across fourth through sixth grade at six different times (fall and spring of each grade). Mean age at baseline was 9.48 ± 44 years. Physical activity was measured using one-day recalls of weekday and weekend activity. An intensity-weighted physical activity recall score was computed by summing a weekday and weekend day recall. Children were categorized as obese or nonobese based on their fourth-grade Body Mass Index (BMI) and sum of tricep and calf skinfold measures (SSKIN). Boys with a BMI ≥20 and a SSKIN ≥ 32 mm and girls with a BMI ≥ 20 and a SSKIN ≥ 36 mm were categorized as obese. Of the sample, 12.4% were classed as obese. A sex-specific 2 × 6 (adiposity by time) repeated measures ANCOVA, holding age and experimental condition constant, was conducted. A significant main effect for adiposity showed that obese boys were less active than nonobese peers, F (1, 253) = 4.20,p =.041. The expected age-related decline in physical activity was found, F (5, 252) = 6.74, p =.001; however, there was no significant difference in the magnitude of this decline for obese and nonobese groups, F (5, 252) =.11, p =.991. There was no significant difference between obese and nonobese girls in overall physical activity, F (1, 239) = 1.33, p =.25. Girls also showed a decrease in physical activity across time, F (5, 238) = 10.65,p <.0005; however, this decline was significantly greater in obese than nonobese girls, F (5, 238) = 2.92, p =.014. This study supports previous findings that participation in physical activity declines with age for both boys and girls. Obese girls decline more in physical activity over three years than nonobese peers. This rapid decrease in physical activity may play a role in the maintenance of adiposity in obese girls.