Evaluation of modified multicompartment models to calculate body composition in healthy males.

The purpose of this study was to develop flexible and accurate multicompartment equations to calculate body composition and compare the results with methods using common two-compartment equations. Twenty-two healthy male volunteers 22-59 y of age were studied. Body volume was measured by underwater weighing (UWW) or with a skinfold caliper, bone mineral by dual-energy X-ray absorptiometry (DXA), and body water by bioelectrical impedance analysis (BIA). The percentage of water and bone mineral in fat-free mass (FFM) had a significant effect on the difference in percentage fat obtained by the two-compartment model compared with a four-compartment model. FFM density was negatively (r = -0.76, P < 0.001) and percentage water in FFM was positively correlated with age (r = 0.75, P < 0.001). The three-compartment model based on field-adapted methods (skinfold thickness + BIA) to calculate percentage body fat correlated significantly with the more complex four-compartment model (UWW + BIA + DXA; r = 0.95, P < 0.001). The advantages of three- and four-compartment equations are that they compensate for differences in body content of bone mineral and water.