Purpose: The aim of the present study was to identify the contribution of nutrition, physical activity (PA), and total energy intake and expenditure on body weight and composition in adolescents. Methods: Body composition, PA, and dietary intakes from 904 Greek adolescents (446 boys and 458 girls; Age: 14.6 ± 1.5 yrs), were evaluated. All participants were assigned into three groups according to their age-sex adjusted Fat Mass Index: (A) Normal weight (N; N = 503), (B) Overweight (OW; N = 253), and (C) Obese (O; N = 148). Results: Significant differences were found for body weight and composition, basal metabolic rate (BMR) expressed per kg of body mass (normal weight children exhibited the highest values), physical-total energy expenditure, and energy balances between the groups (η2: 0.138 to 0.657; p < .05). In contrast, no differences were found for macronutrients' and total energy intakes, food consumption and quality (η2: 0.002 to 0.099; p > .05) between the three examined groups. Strong, negative correlations were observed between body weight, body fat percentage, PA, and total energy expenditure (r: -0.311 to -0.810; p < .001). Lower, negative correlations were found between body weight, body fat percentage, and macronutrients' daily intakes (r:-0.235 to -0.432; p < .05). BMR and total energy expenditure had strong, negative relative strengths for the determination of body weight and fat percentage. Conclusions: In conclusion, it seems that BMR, PA, and total daily energy expenditure expressed per body weight and not the nutritional and total energy intakes, were the primary determinant parameters of body composition and weight in adolescents.
Keywords: Basal metabolic rate; dietary intake; free fat mass; obesity.