Health‐related fitness in adolescents: underweight, and not only overweight, as an influencing factor. The AVENA study

This study investigated differences in health‐related fitness (20‐m shuttle run, handgrip, bent arm hang, standing long jump, shuttle run 4 × 10 m and sit and reach tests) in 2474 Spanish adolescents (1196 boys and 1278 girls; age 13–18.5 years) classed as underweight, normal weight, overweight or obese according to body mass index. Body fat and fat‐free mass were derived from skinfold thickness. The prevalence of underweight was higher than obesity in girls (4.8% vs 3.0%, respectively; P <0.05) and the opposite in boys (3.9% vs 5.8%, respectively; P <0.05). Underweight was associated with a higher performance in the bent arm hang test in girls ( P <0.05) and a lower performance in handgrip in both genders ( P <0.01) compared with normal weight. Overweight and obese adolescents presented a lower performance in 20‐m shuttle run, bent arm hang, standing long jump and shuttle run 4 × 10 m tests ( P <0.001), but a higher performance in handgrip strength ( P <0.001) compared with normal weight. In weight‐bearing tests, the association became non‐significant after adjusting for fat mass. In conclusion, not only overweight and obesity but also underweight seem to be determinants of health‐related fitness in adolescents. The associations could be related to differences in body composition.