BODY-COMPOSITION ASSESSMENT BY DUAL-ENERGY X-RAY ABSORPTIOMETRY IN SUBJECTS AGED 4-26 Y

This cross-sectional study describes the body composition of 265 norma l subjects (137 males and 128 females) aged 4-26 y determined by dual- energy x-ray absorptiometry (DXA). Lean tissue mass (LTM) and bone min eral content (BMC) increased with age in females until 13.4 and 15.7 y , respectively, and in males until 16.6 and 17.4 y, respectively. A st rong relation between LTM and BMC was found for each sex (r = 0.98, P = 0.0001 for males; r = 0.98, P = 0.0001 for females). DXA percent bod y fat (%BFDXA) increased with age in females (r = 0.52, P < 0.001) but not in males and was higher in females than in males at all ages. Tru nk to leg fat ratio (TLFR) was calculated as DXA trunk fat/leg fat. In post-pubertal age the TLFR was higher in males than in females (1.01 +/- 0.23 and 0.75 +/- 0.16, P = 0.001), but there was no sex differenc e in younger children. DXA weight underestimated scale weight by a mea n of 0.83 kg. %BFDXA correlated with %BF by skinfold thickness measure ment with good agreement for males but overestimated %BF by skinfold t hickness for females. These normative data for body composition demons trate significant sex differences in all body compartments after the p ubertal years.