[Determining of body mass index in adolescents from public schools in Piracicaba, São Paulo State].

The objective of this study was to assess determining factors of body mass index (BMI) in adolescents enrolled in public schools in Piracicaba, São Paulo. The sample had 328 adolescents from both genders; minimum age was 10 years old. We have assessed weight, height, sexual maturity, physical activity, and diet. A multiple linear regression model was used to assess the association between independent variables and BMI. While girls considered physically active presented greater mean BMI than those insufficiently active, boys did not present statistical difference between mean BMI among those active and those insufficiently active. Sexual maturity was a determinant for BMI, for both genders, reinforcing the idea that it is essential to take this variable into account in studies that assess the nutritional situation in adolescents. We believe that the methods used in the present study, which are normally used in similar surveys, have important limitations to assess the influence of variables such as the level of physical activity and food intake on the BMI of adolescents. Thus, it is important to improve these methods and adopt them in further studies.