The Impact Of Physical Activity On Body Composition Indices Among Mexican Adolescents: A Cross-sectional Analysis

In Mexico, the incidence of obesity in adolescents is 41.1%. The Body Mass Index (BMI) is conventionally utilized as an anthropometric index. As lacks the specificity to discern adipose tissue mass from lean muscle mass, bioelectrical impedance analysis (BIA) is advocated as a more nuanced method. PURPOSE: To compare the BMI with BIA for assessing body composition—specifically adipose tissue mass and lean muscle mass—in Mexican adolescents, stratified by their level of physical activity (PA). METHODS: The BMI of a group of 63 adolescents (34 Females, 29 Males) was computed utilizing weight and height (F: 61.2 ± 18.10 kg, 161.5 ± 6.15 cm; M: 74.6 ± 13.38 kg, 175.5 ± 7.6 cm). Body composition parameters, including adipose tissue mass (kg) and lean muscle mass (kg), were derived via BIA (InBody 120). PA levels were quantified using the International Physical Activity Questionnaire (IPAQ). Descriptive and t-test statistics were performed using JAMOVI 2.4.8 (p < .05). RESULTS: Gender-based comparative analysis did not indicate statistical disparities in BMI (F: 23 ± 6.12 vs. M: 24.3 ± 4.25): t (61) = -.933, p = .355, d = -.235, 95% CI [-.732, .262] or adiposity (F: 21.4 ± 11.72 kg vs. M: 18 ± 9.73 kg): t (61) = 1.249, p = .216, d = .315, 95% CI [-.184, .813] but revealed significant disparities in muscularity (F: 21.5 ± 4.25 kg vs. M: 31.8 ± 4.64 kg): t (61) = -9.154, p < .001, d = -2.313, 95% CI [-2.951, -1.665]. Stratification by PA dichotomized subjects into active (AC; n = 38) and inactive (IN; n = 25) cohorts, revealing discrepancies in body mass (AC: 71.6 ± 17.16 kg vs. IN: 61.0 ± 15.89 kg): t (61) = 2.446, p = .017, d = .634, 95% CI [.115, 1.150], BMI (AC: 25.1 ± 5.33 vs. IN: 21.2 ± 4.46): t (61) = 3.060, p = .003, d = .788, 95% CI [.261, 1.309] and lean muscle mass (AC: 27.7 ± 6.02 kg vs. IN: 24.1 ± 7.40 kg): t (61) = 2.088, p = .041, d = .537, 95% CI [.022, 1.049] but not in adipose tissue mass (AC: 21.8 ± 12.33 kg vs. IN: 16.9 ± 7.62 kg): t(61) = 1.751, p = .085, d = .450, 95% CI [-.061, .960]. CONCLUSION: Notable sexual dimorphism was evident in body composition measures, with PA status further stratifying distinctions in BMI and muscularity. The enhanced mass and BMI observed in physically active adolescents could be attributed to increased lean muscle accrual, a testament to the limitation of traditional metrics like BMI which do not discriminate between body composition segments.