This $149,860 project over three years is a cluster-randomized trial in 12 primary schools in urban areas of Beijing of a school-based policy intervention aimed at promoting a healthy diet and increased physical activity. The school-specific intervention policies, which will be based on the results of evaluations conducted during the pilot study, will be developed with the active participation of school principals, teachers, doctors and canteen staff. The main outcomes-to be assessed after 12 months-will be changes in BMI and other physical parameters in 150 students in grades 3-5 at each of the 12 schools.