Physical activity intensity and risk of overweight and adiposity in children

Physical activity recommendations for children focus on duration of activity and underemphasize intensity.

To evaluate the relationship between physical activity (intensity and duration) and the odds of being overweight, >20% body fat and >25% body fat.

Body fat, BMI and physical activity (accelerometry) were measured in children (n = 251) aged 8-10 years. Physical activity was quantified as time in moderate physical activity (MPA) and vigorous physical activity (VPA).

Prevalence of overweight and obesity were 18 and 11.6%, respectively. Regression indicated that VPA, not MPA, is associated with body fat (r = 0.35, P < 0.001) and BMI (r = 0.26, P < 0.001). Odds ratio demonstrated a significant impact of MPA and VPA on body composition. Children performing < or =5 min/day of VPA are 4.0 times more likely to have > or =20% body fat (P < 0.001), 2.9 times more likely to have > or =25% body fat (P < 0.05) and 5.2 times more likely to be classified as overweight (P < 0.01) compared to children performing > or =15 min/day. Those performing < or =15 min/day of MPA vs. >45 min/day MPA are at 4.2 increased odds of having > or =20% body fat (P < 0.001), and 3.0 increased odds of having > or =25% (P < 0.01).

Lower durations of both MPA and VPA are associated with increased odds of overweight and adiposity. Forty-five minutes of MPA and fifteen minutes of VPA were associated with reduced body fat and BMI. We recommend that these amounts are used to develop minimum physical activity intensity guidelines for the prevention and treatment of obesity.