Objective: To assess the efficacy of a school-based intervention programme to reduce the prevalence of overweight in 6 to 10-year-old children. Design: Cluster-randomized, controlled study. Subjects: A total of 3135 boys and girls in grades 1-4 were included in the study. Methods: Ten schools were selected in Stockholm county area and randomized to intervention (n ¼ 5) and control (n ¼ 5) schools. Low-fat dairy products and whole-grain bread were promoted and all sweets and sweetened drinks were eliminated in intervention schools. Physical activity (PA) was aimed to increase by 30 min day À1 during school time and sedentary behaviour restricted during after school care time. PA was measured by accelerometry. Eating habits at home were assessed by parental report. Eating disorders were evaluated by self-report. Results: The prevalence of overweight and obesity decreased by 3.2% (from 20.3 to 17.1) in intervention schools compared with an increase of 2.8% (from 16.1 to 18.9) in control schools (Po0.05). The results showed no difference between intervention and controls, after cluster adjustment, in the longitudinal analysis of BMIsds changes. However, a larger proportion of the children who were initially overweight reached normal weight in the intervention group (14%) compared with the control group (7.5%), P ¼ 0.017. PA did not differ between intervention and control schools after cluster adjustment. Eating habits at home were found to be healthier among families with children in intervention schools at the end of the intervention. There was no difference between children in intervention and control schools in self-reported eating disorders. Conclusions: A school-based intervention can reduce the prevalence of overweight and obesity in 6 to 10-year-old children and may affect eating habits at home. The effect of the intervention was possibly due to its effect on healthy eating habits at school and at home rather than on increased levels of PA.

The decline in PA in children may start already at the age of 6 yr. The school setting may be an important arena for targeting activity levels in girls because the difference in PA levels between girls and boys is most pronounced during school time. In both girls and boys, PA levels are disproportionally low during weekends and might be important targets for interventions aimed to increase PA.

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