In 2008, under the National Plan for Health Promotion and Community Plan for the Promotion of Health, actions to address school obesity by intervening with the Global Strategy Against Obesity schools with the highest obesity prevalence focusing on kindergarten levels (school children between 5-6years) and first grade (students between 6-7 years). The actions of the Community Plan for the Promotion of Health in selected schools of Valparaiso were evaluated. The objectives of this intervention were: 1) assess the nutritional status of children from the participating levels, 2) gather background information on knowledge and behaviors related to food, nutrition and lifestyle in school and 3) identify strengths and difficulties facing the implementation of health policies at local level. We performed a descriptive, non-experimental, non-random convenience sample, which included 267 schools. Results: It was detected 18.8% obesity in the transition level (kindergarten and 27% in the first grade evaluated according to Technical Standards of the Ministry of Health of Chile based on 2006 WHO reference tables. In order to assess knowledge and behavior, we developed and applied the tools "Caritas" and "Healthier Snacks" observing 77% and 87% and 90% and 64% of correct associations for knowledge and behaviors, respectively. Facilitators: cooperative work and valuation from education. Barriers: outdated actions altering school curriculum planning. Figures of malnutrition by excess and the difficulty to reverse this reality require programs to in identify nutritional knowledge and eating behaviors of the population.