Body Fatness and Sexual Saturation Status
Purpose: (1) to characterize the maturation status on the basis of breast development in the girls and genital development in the boys, resp. on occurrence or non-occurrence menarche or spermarche; (2) to study the sexual differences in body components during the puberty, (3) to analyze body components in children belonging to the same age group, but different maturation stages and to the various of maturation indicators, but differing in age.
Subjects: The subjects of the present subsample of the 2nd national cross-sectional study were such children that had already begun pubertal development. The chronological age of the girls (n = 2673) and boys (n = 2869) ranged between 10.0 and 16.0 years.
Methods: The girls were subdivided by the maturation stages of the breast, while the boys by those of the genitals. Sexual maturation was assessed visually and rated by Tanner's suggestions (1962). Percentage of body fat was estimated by model of two components (Durnin and Rahaman 1967, Siri 1956), while masses of body components (fat, bone, muscle and residual mass) were assessed by the Drinkwater and Ross' (1980) four-component anthropometric fractionation method. Multiple comparisons of the means were tested by Scheffe's formula at the 5% level.
Results: Sexual differences in body composition, present already in childhood, became more accentuated during puberty, due mainly to growing fat content in the girls and to increasing lean body mass in the boys. In the females early maturers were heavier and contained more fat than less mature girls. This increase relative and absolute fat mass was proportionate to weight gain. In the males increasing fat mass lagged behind the gain in lean body mass both with advancing age and maturity status.
Conclusion: Body composition and maturity status are closely interrelated in both genders while gender-specific tendencies increase dimorphism and the several factors making up the differences between maturation types. Fat content was greater in both sexes in the early maturers. Also the developmental rate of prepubertal fat accumulation was faster in the early maturers when compared to those maturing later. Standards for the age change of body composition can therefore inform us not only about the development of bone, muscle and fat in childhood, but also allow a short-range prediction of pubertal events.