Introduction: The consequences of adolescents obesity is well documented in many systems and the most common and harmful are metabolic syndrome and cardiovascular disease. Recently, some studies have suggested that sleep deprivation could play a role in obesity occurrence. We aimed investigate the relationship between sleep patterns and excess of body weight in adolescents. Methods: between August and October of 2008, adolescents (301 boys and 287 girls) from both sexes (mean age 12,6±0,9) who attended afternoon classes from 1pm to 5.30 pm, participated in the study. The variables measured were body mass index (BMI), waist circumference (WC) and body fat percentage. Bedtime and wake time on school days and weekends were evaluated by a questionnaire. Sleep duration were calculated from these data. Nonparametric correlation analyses were used to investigate associations between sleep and anthropometric variables. Results: Mean sleep duration was 10 hours with no significant differences between school days and weekends (p>0,53). There was an inverse correlation between sleep duration and three anthropometric variables. For bedtime and wake time there were no significant associations. When analyzing by group, significant associations between waist circumference/BMI (r=-0.11 for both) and sleep duration occurred only in boys. Discussion: the results evidence a tendency that who sleep less is probably more susceptible of being with a higher BMI, WC and body fatness. However, the power of associations are too small and it contrasts with strong correlations observed in previous studies. The longer sleep duration of these adolescents, related to afternoon school schedule, suggests an absence of sleep deprivation in many of them and could explain, at least partially, the results. Conclusion: These results are part of on ongoing follow-up study which will investigate changes in sleep-wake patterns and body weight after the transition to morning schedules. These data will be compared with those from adolescents that will keep the same school schedule. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil
Rossi et al. (Thu,) studied this question.