OBJECTIVE: To examine the effect of age on the relationship between fat-free mass (FFM) and fat mass ( FM), and fat-free mass index (FFMI) and fat mass index (FMI) by applying body composition chart analysis on pre- and postadolescent Japanese subjects.
SUBJECTS AND METHOD: A sample of 516 children (244 boys and 272 girls) ranging in age from 11 to 17 y and 840 adults ( 288 male and 552 female subjects) ranging in age from 18 to 59 y were studied to determine a body composition by an underwater weighing method. FMI and FM were put on an x- and y-axis in body composition chart 1, and FFMI ( FFM/height(2)) and FMI (FM/height(2)) were taken on an x- and y-axis in body composition chart 2.
RESULTS: In body composition chart 1, the plots for male subjects stayed flat from 11 to 14 y and after that a steady growth of FFM concurring with the FM growth was observed. During the adult stage, steady increments of FM and gradual decreases of FFM were observed. In body composition chart 2, steady increases of FFMI and gradual decreases of FMI were indicated in the male preadolescent period. In the adult stage, FFMI decreased year by year, although the FMI continued to increase. In female subjects, a conspicuous increase of FMI was observed throughout all periods of the present subjects. After middle age, the decline of FFMI was characteristically demonstrated in the chart.
CONCLUSION: The relationships between FFM and FM are characteristically delineated on the body composition charts demonstrating clear gender differences. The change of body mass index was not reflecting the change of adiposity level in male subjects, although it was occurring along with the changes of the adiposity level in female subjects.