Growth and growth velocity of lean body mass and fat in adolescent boys.

Beginning at age 10 years, height, weight, body density, and bone age of 40 normal boys were measured yearly over a period of 8 years. From body density, lean body mass and body content of fat were calculated. Values for all measurements are included in the Appendix and mean values, including those for lean body mass and percentage of body fat, are presented for each year in Table 1. Coefficients of correlation between measurements made during the first and eighth years of study were high for height (0.68), weight (0.50), and lean body mass (0.60), but relatively low for body fat (0.25). Correlation coefficients between the various parameters in a given year are presented in Table 2. The maximum yearly increment in height, weight, and lean body mass of individual subjects coincided in time. The respective mean values for the year of maximum growth were 9.4 cm, 8.1 kg, and 7.5 kg. Throughout the growth spurt, the contribution of fat to increase in body weight was small. It may be concluded that, next to height, the absolute amount of lean body mass demonstrates the most constant trend of development during adolescence.