SPECIAL COMMUNICATIONS Methods Comparison of the BOD POD with the four- compartment model in adult females

study was designed to compare the accuracy and bias in estimates of total body density (Db) by hydrostatic weighing (HW) and the BOD POD, and percent body fat (%fat) by the BOD POD with the four-compartment model (4C model) in 42 adult females. Furthermore, the role of the aqueous and mineral fractions in the estimation of body fat by the BOD POD was examined. Methods: Total body water was determined by isotope dilution (2H20) and bone mineral was determined by dual-energy x-ray absorptiometry. Db and %fat were determined by the BOD POD and HW. The 4C model of Baumgartner was used as the criterion measure of body fat. Results: HW Db (1.0352 g·cm3) was not statistically different (P 0.35) from BOD POD Db (1.0349 g·cm3). The regression between Db by HW and the BOD POD significantly deviated from the line of identity (Db by HW 0.90 Db by BOD POD 0.099; R2 0.94). BOD POD %fat (28.8%) was significantly lower (P 0.01) than %fat by the 4C model (30.6%). The regression between %fat by the 4C model and the BOD POD significantly deviated from the line of identity (%fat by 4C model 0.88 %fat by BOD POD 5.41%; R2 0.92). BOD POD Db and %fat showed no bias across the range of fatness. Only the aqueous fraction of the fat-free mass (FFM) had a significant correlation with the difference in %fat between the 4C model and the BOD POD. Conclusion: These data indicate that the BOD POD underpredicted body fat as compared with the 4C model, and the aqueous fractio