DXA-Derived Body Composition Across the Mexican National Football Pathway by Sex, Age Category, and Playing Position

Background/Objectives: Sex- and category-specific body-composition references are scarce for Latin American and female football players. We used dual-energy X-ray absorptiometry (DXA), which quantifies lean soft tissue, fat, and bone mineral content (BMC) regionally in one low-dose scan, to describe body composition across Mexican national squads and to explore associations with playing position. Methods: We analyzed 272 DXA records acquired in 2026 under one standardized protocol (females: n = 133, under-15 [U15] to senior; males: n = 139, under-14 [U14] to senior) using 95% confidence intervals and height-adjusted, sex-stratified linear models with heteroscedasticity-consistent (HC3) standard errors and Holm correction. Results: Senior squads had 8.83 kg (females) and 13.23 kg (males) more total lean mass than the youngest category (Hedges’ g > 2) and 6.32 and 2.59 percentage points less body fat. Male fat mass was similar across categories (10.4–11.7 kg), suggesting that the lower body-fat percentage of older male squads reflected greater lean mass; in females, it reflected both greater lean mass and lower fat mass. Category remained associated with lean mass and BMC after height adjustment (Holm-adjusted p < 0.001) but was not significantly associated with male body-fat percentage (p = 0.118). No association between position and body composition was observed in females; male forwards had more lean mass and less fat than goalkeepers. Conclusions: These preliminary cross-sectional references allow staff to benchmark players against their own squad and to flag atypical lean or bone values for multidisciplinary review; they are not developmental trajectories or body-composition targets.