Comparison of four methods to assess body composition in women.

The purpose of this study was to compare the accuracy of four methods to assess body composition of women. Seventy-seven Caucasian women [mean (+/- SD) age: 31.8 +/- 8.6 years; mass: 59.5 +/- 9.1 kg; stature: 162.4 +/- 6.9 cm; Quetelet Index: 22.5 +/- 3.1 kg/m2] were tested for percent body fat (%BF) with hydrostatic weighing (HW), near-infrared spectrophotometry (NIR), bioelectrical impedance analysis (BIA), and seven-site skinfolds (7-SFs). Compared to %BF with HW (24.9 +/- 6.5%), an analysis of variance revealed no mean differences (P > or = 0.05) among %BF with NIR (26.0 +/- 5.5%), BIA (25.7 +/- 5.8%) and 7-SFs (24.0 +/- 6.0%). The correlations between %BF with HW and NIR, BIA and 7-SF were r = 0.47, r = 0.77, and r = 0.79, respectively (P < or = 0.05), and prediction errors (SEE) were 5.8%, 4.2%, and 4.1%. Comparisons of %BF obtained from machine readings versus those computed from the manufacturer's equation indicated significant differences for the BIA (machine 25.7%, equation 27.8%) and NIR (machine 26.0%, equation 21.5%) methods. We concluded that although the mean %BF differences were small among the four methods, the large SEE values may allow the use of BIA and 7-SFs but not NIR. Inaccuracies of machine readings versus equation-computed %BF indicate that BIA and NIR variables and/or constants in the equations supplied are not identical to those used in machine-generated calculations.