Body composition in children and Tanner's stages: a study with dual-energy x-ray absorptiometry

Total body bone mineral content (TBBM), body fat content (BF), and fat-free mass (FFM) were measured in 154 children using dual-energy x-ray absorptiometry (DEXA). Total body calcium level (TBCa) was calculated from TBBM. Children were divided into groups according to Tanner's stages 1, 2, 4, and 5. Children in stage 3 were not included in the study in order to better differentiate between prepubertal and postpubertal individuals. We did not find differences in TBBM, TBCa, BF, and FFM between Tanner's stages 1 and 2 or between sexes. TBBM and TBCa in stages 4 and 5 were lower in girls than in boys (P < .001 and P < .01, respectively); no differences were observed between girls of both groups, although boys showed significant differences (P < .05). FFM for both sexes was lower in stages 1 and 2 than in stages 4 and 5. Girls showed lower FFM (P < .001) than boys in stages 4 and 5; FFM was higher in boys in stage 5 than in those in stage 4 (P < .005), and the same was true for girls (P < .002). Boys in stage 4 had less BF than girls (P < .005), and the same was true for stage 5 (P < .001). Girls in stages 4 and 5 had greater BF than those in stages 1 and 2 (P < .001). These differences suggest that as boys go through puberty, both TBBM and FFM continue to increase, while in girls only BF and FFM increase. These data indicate clear sex differences in somatic postpubertal development.