Cross-validation of modified fatness-specific bioelectrical impedance equations.

The Segal fatness-specific bioelectrical impedance (BIA) equations are useful for predicting fat-free mass (FFM). Stolarczyk et al. Proposed a modified method of averaging the two equations for individuals who are neither lean nor obese, thus eliminating the need to know % BF a priori. To cross-validate this modification, we compared FFM determined using the averaging method versus hydrostatic weighing for 76 adults. Per the averaging method, accuracy for males was excellent (r =.91, SEE = 2.7 kg, E = 2.7 kg), with 78% of individuals within +/- .5% BF predicted by hydrostatic weighing. Accuracy for females was lower (r =.88, SEE = 3.0 kg, E = 3.1 kg), with % BF of 51% within +/- 3.5% of the reference method. The relative ease and practicality of the averaging method and the results of this study indicate this method may be useful with a diverse group.