[Body composition (densitometry-hydrostatics), skinfold thickness, BMI and their relationships in junior high school girls].

A study was conducted to evaluate body composition (Hydrostatics = Under-Water Weighing), skinfold thickness, and BMI in 97 junior high school girls, aged 12 to 15, in Nagasaki City. Body density was measured by under-water weighing, and the two compartments--fat weight (Fat) and lean body mass (LBM, or fat free weight: FFW)--were calculated using the formulas of Brozek et al. The results were as follows; 1. Mean values of body density were 1.0501 in first grade girls, 1.0476 in the second grade, and 1.0466 in the third grade. 2. Mean values of percentage body fat (% Fat) were 21.1% in the first grade, 22.1% in the second and 22.5% in the third. 3. Lean body mass (LBM) and LBM/Height increased significantly with advance from the first to the third grade. 4. The correlation coefficient between percent body fat and the sum of two skinfold thicknesses, the sum of three skinfold thicknesses, or the sum of seven skinfold thicknesses were 0.81, 0.80, and 0.82 respectively and all statistically significant (p < 0.001). 5. The correlation coefficient between BMI and the sum of two skinfold thicknesses, the sum of three skinfold thicknesses (r = 0.841) or the sum of seven skinfold thicknesses were 0.85, 0.84, and 0.84 respectively, and all statistically significant (p < 0.001). 6. Mean values of BMI, WSR, ASR, and WHR in all subjects (n = 97) were 19.6, 0.72, 0.39 and 0.43 respectively.