School-based obesity prevention in Chilean primary school children: methodology and evaluation of a controlled study.

OBJECTIVE: To assess the impact of a 6 months nutrition education and physical activity intervention on primary school children through changes in adiposity and physical fitness. DESIGN: Longitudinal school-based controlled evaluation study. SUBJECTS: Children from 1st to 8th grade, 2141 in intervention and 945 in control schools. INTERVENTION: Nutrition education for children and parents, 'healthier' kiosks, 90 min of additional physical activity (PA) weekly, behavioral PA program and active recess. MEASUREMENTS: Adiposity indices (BMI, BMI Z-score, triceps skinfold thickness (TSF), waist circumference and physical fitness (20 m shuttle run test and lower back flexibility). RESULTS: Positive effect on adiposity indices (except TSF) was observed in boys (P<0.001 for BMI Z), while both physical fitness parameters increased significantly in both boys (P<0.001 for each test) and girls (P<0.0001 for each test). A differential effect in BMI Z was observed according to baseline nutritional status. CONCLUSIONS: This intervention showed a robust effect on physical fitness in both genders and decreased adiposity only in boys.