[Effectiveness of a dietary and physical activity intervention to prevent obesity in school age children].

BACKGROUND With the aim of contributing to he Healthy Goal 2010 of reducing significantly the prevalence of childhood obesity we developed and implemented during 2003 and 2004, a school-based obesity prevention intervention which included nutrition education and the promotion of physical activity. AIM To report the results of the intervention. MATERIAL AND METHODS The sample included 1760 children (1st to 7th grade) from 3 elementary public schools in Casablanca (experimental group) and 671 from a similar school located in Quillota, a neighboring city (control). Primary outcomes were body mass index (BMI) Z score, the mile and shuttle-run tests and obesity prevalence. We also compared changes in waist circumference and triceps skinfold between both groups. Effectiveness of the intervention was assessed by analyzing separately the group *age* time interaction for the first 3 outcomes (follow-up-baseline), using a mixed model of covariance and by comparing variations in obesity prevalence between both groups. RESULTS There was a significant decline in BMI Z scores in experimental schools for both genders, but greater in boys (p <0.001 versus p =0.0034 in girls), while in controls, BMI Z scores increased. Obesity prevalence declined significantly in experimental schools; from 17 to 12.3% and from 14.1 to 10.3% in boys and girls respectively, while in the control group, it remained unchanged. Also, triceps skinfold in girls from Casablanca increased significantly less than that of control girls. CONCLUSION This intervention proved that it is possible to reduce significantly the prevalence of obesity in Chilean schoolchildren attending public elementary schools.