Body composition in white adults by dual-energy x-ray absorptiometry, densitometry, and total body water.

Percent body fat (%BF) and fat-free mass (FFM) were determined in 151 adults from the Fels Longitudinal Study by total body scans with a Lunar DPX (DXA), by underwater weighing and residual lung volume with a two-compartment model using body density (Dens), and total body water (TBW) using deuterium dilution. For the DPX, the medium scan mode ensures precision up to 100 kg body wt and for a ratio of weight to stature < or = 0.7214. Because of these specifications, 15% (n = 23) of the original sample of 151 were excluded. Results for 78 women and 50 men are presented. %BFTBW was significantly (P < 0.05) less than %BFDens in women (mean difference 2.7 +/- 4.2%) and %BFDXA in men (mean difference 2.2 +/- 4.3%). No other significant intermethod differences were observed for %BF and FFM estimates. Pairwise regressions showed the lowest SEEs for %BFDens regressed vs %BFDXA (2.3% for men, 3.2% for women) and for FFMDens vs FFMDXA (2.2 kg for men, 1.9 kg for women). For each sex, reliability analyses and limits of agreement for body composition estimates showed less agreement between TBW and either Dens and DXA than between Dens and DXA.