Childhood obesity in Chile has been recognized as a public health problem. In 2006, we developed a school-based obesity prevention pilot project to intervene during 5 months preschool and schoolchildren from 1st to 4th grades attending 7 public schools located in a district of Santiago, Chile of medium-low and low SES. The objective of this project was to evaluate the feasibility of implementing a longer intervention giving recommendations to the educational authorities to better implement it. We trained teachers to apply educational activities ( in nutrition and physical activity) for the children in the 7 schools, but additionally in 4 of these schools, teachers of those grades participated in a Counselling program on healthy lifestyle applied individually, anthropometric evaluation and blood tests. The initiatives were evaluated on a sample of 522 schoolchildren (nutritional status and physical fitness), 38 teachers with Counselling (BMI, waist circumference or WC, blood sugar, HDL, triglycerides, cholesterol) and 19 teachers with no counselling (BMI and WC). Additionally, we evaluated the quality of PE classes. The results on the children show a trend on only the younger ones to decrease the % obesity, improving significantly their physical fitness. In teachers with counselling, a trend toward decreasing BMI and WC was observed, while biochemical parameters remained unchanged. We showed that it is feasible to implement a longer intervention recommending improving the quality of PE classes and allowing more time to train teachers and for individual counselling.