Associations of changes in BMI and body fat percentage with demographic and socioeconomic factors: the ELANA middle school cohort.

Adolescents who experienced better socioeconomic conditions, especially boys, were more likely to have greater increases in body fat indicators. Our findings contribute to the better understanding of BMI trajectories and body composition changes during puberty, as well as demonstrates the relationship between socioeconomic variables and adiposity indicators among adolescents in middle-income countries.