ABSTRACT The object of the present study was to carry out a literature review to analyze the influence of physical activity and dietary behavior on body mass index in school-age children and adolescents. A search was carried out using the PubMed and LILACS databases, in which 1,412 articles were found. After application of inclusion and exclusion criteria, 17 studies were selected for qualitative analysis. Overweight and obesity were related with incorrect dietary habits (skipping breakfast, consumption of foods with high fat contents and high-sugar soft drinks), low levels of physical activity and long hours devoted to sedentary activities (playing video games or watching TV) were also related.