Objective: to analyze the impact of educational software on the behavior of adolescents about obesity prevention in two public schools of Divinópolis-MG. Method: uncontrolled clinical trial involving 238 adolescents, in the city of Divinópolis, MG, Brazil. Between June and October 2018, weight and height were measured, 24-hour dietary recall was performed, physical activity level was verified, socioeconomic classification and the stage of readiness for behavioral change was evaluated. The McNemar test was used to compare the qualitative variables. For the effect of the intervention on the quantitative variables, the Generalized Estimating Equations model was used. In the intervention, the educational game Healthy Running was used, developed for this study. Data were collected before and two months after the intervention. Results: among the participants, 62.6% are female, with a median age of 16.7 years, ranging from 15 to 19 years. Regarding the nutritional situation before the intervention, 18.5% had excess weight. As to the level of physical activity is concerned, 50.4% were classified as active. After the intervention, the z-score of body mass index for males showed a significant improvement (p<0.000), as well as the level of physical activity (p<0.001). Conclusion: the use of the educational game was valid and presented relevant results in improving the adolescents' behavior regarding food and physical activity. The use of the educational game can be considered appropriate to support education in the health area.