Proposta de um índice alternativo ao índice de massa corporal tradicional para adolescentes

Abstract

Nutritional status assessment is a cornerstone of public health and clinical practice, but commonly used methods such as Body Mass Index (BMI) have important limitations. Since BMI does not distinguish between fat mass and lean mass, it may lead to misinterpretation of body composition, particularly in adolescents, whose body composition undergoes significant changes during growth. This highlights the need for more refined tools capable of providing a more accurate characterization of metabolic risk. The present study aimed to propose the Corrected Body Mass Index (CBMI) as a more sensitive and precise alternative to traditional BMI in adolescents. A cross-sectional observational study was conducted in a school setting, with approval from the Ethics Committee of the Faculty of Sport, University of Porto (approval no. [CEFADE 25 2023]). The sample consisted of 332 adolescents (both sexes), aged 13-18 years. Anthropometric and body composition data were collected through bioelectrical impedance analysis, and CBMI was calculated. CBMI showed greater discriminative capacity than BMI, identifying significant differences between sexes and metabolic risk profiles, with greater heterogeneity observed among girls. Bland-Altman analysis revealed systematic discrepancies between the indices, confirming that they are not interchangeable and that CBMI provides relevant additional information. Findings suggest that CBMI may represent a more accurate tool for screening excess adiposity in adolescents, with potential application in clinical, school, and epidemiological settings. However, longitudinal studies with larger, representative samples are needed to validate its predictive utility and to establish sex-specific cut-off points, considering physiological differences in fat distribution between boys and girls, in order to avoid misclassification bias.