Improvement of Fitness, Body Composition, and Insulin Sensitivity in Overweight Children in a School-Based Exercise Program

BACKGROUND: Obesity and poor physical fitness constitute a health problem affecting an increasing number of children. Causes include a pervasive "toxic" environment that facilitates increased caloric intake and reduced physical activity. An effective strategy for prevention and treatment of childhood obesity likely includes a collaborative effort in the school setting. OBJECTIVE: To determine whether a school-based fitness program can improve body composition, cardiovascular fitness level, and insulin sensitivity in overweight children. DESIGN: Fifty overweight middle school children with a body mass index (BMI) above the 95th percentile for age were randomized to lifestyle-focused, fitness-oriented gym classes (treatment group) or standard gym classes (control group) for 9 months. Children underwent evaluation of fasting insulin and glucose levels, body composition by means of dual energy absorptiometry, and maximum oxygen consumption (V0(2)max) treadmill testing at baseline (before the school year) and at end of the school year. SETTINGS: Rural middle school and an academic children's hospital. MAIN OUTCOME MEASURES: Baseline test results for cardiovascular fitness, body composition, and fasting insulin and glucose levels. RESULTS: At baseline, there were no differences between groups before intervention (values for age, 12 +/- 0.5 years all results, mean +/- SD; BMI calculated as weight in kilograms divided by the square of height in meters, 31.0 +/- 3.7; percentage of body fat, 36.5% +/- 4.6%; lean body mass, 41.4 +/- 8.6 kg; and V0(2)max, 31.5 +/- 5.1 mL/kg per minute). Compared with the control group, the treatment group demonstrated a significantly greater loss of body fat (loss, -4.1% +/- 3.4% vs -1.9% +/- 2.3%; P = .04), greater increase in cardiovascular fitness (V0(2)max, 2.7 +/- 2.6 vs 0.4 +/- 3.3 mL/kg per minute; P<.001), and greater improvement in fasting insulin level (insulin level, -5.1 +/- 5.2 vs 3.0 +/- 14.3 microIU/mL -35.4 +/- 36.1 vs 20.8 +/- 99.3 pmol/L; P = .02). CONCLUSIONS: Children enrolled in fitness-oriented gym classes showed greater loss of body fat, increase in cardiovascular fitness, and improvement in fasting insulin levels than control subjects. The modification to the school physical education curriculum demonstrates that small but consistent changes in the amount of physical activity has beneficial effects on body composition, fitness, and insulin levels in children. Partnering with school districts should be a part of a public health approach to improving the health of overweight children.