To investigate body composition and associated factors in adolescents undergoing long-term regular sports training.

This prospective longitudinal cohort study employed convenience sampling to recruit adolescents receiving structured athletic training at Jining Sports Training Center in June 2023. Baseline measurements included height, weight, body mass index (BMI), blood pressure, heart rate, waist circumference, and hip circumference. Questionnaires assessed sleep duration, screen time, and household income. Follow-up measurements in June 2024 repeated these assessments while adding bioelectrical impedance analysis for body composition (lean mass, skeletal muscle mass, fat mass, and body fat percentage). Linear regression models examined associations between training type (direct-contact vs. non-contact sports) and follow-up body fat percentage, BMI, and waist circumference as dependent variables, adjusting for covariates.

The study included 110 adolescents (39 female, 71 male) with median age 13.21 years (IQR: 12.46-14.33). Participants comprised 65 direct-contact and 45 non-contact athletes. Baseline prevalence rates were 27.27% for overweight/obesity, 24.55% for elevated waist circumference, and 16.36% for elevated blood pressure. At follow-up, corresponding rates were 24.55%, 26.36%, and 13.64% respectively. The elevated blood pressure subgroup showed significantly higher waist circumference (P=0.034), elevated waist circumference rate (P=0.011), and body composition weight (P=0.049) compared to normotensive peers. Longitudinal analysis revealed 56.36% of participants increased BMI and 63.64% increased waist circumference. Adjusted linear regression demonstrated significant inverse associations between direct-contact training and body fat percentage (β=-6.57, 95% CI: -9.37 to -3.78, P < 0.001), BMI(β=-1.30, 95% CI: -2.50 to -0.11, P=0.036), and waist circumference(β=-2.31, 95% CI: -4.40 to -0.22, P=0.034).

Despite regular athletic training, substantial proportions of adolescents exhibited overweight/obesity, abdominal obesity, and elevated blood pressure, warranting clinical attention. Training modality appears to influence body composition changes, with direct-contact sports associated with more favorable adiposity-related outcomes.