Association of bioelectrical resistance with estimates of fat‐free mass determined by densitometry and hydrometry

Abstract

Abstract The relationship of whole‐body electrical resistance (WBR) to fat‐free mass, derived from densitometry (FFM Db ), hydrometry (FFM TBW ), and densitometric fat‐free mass corrected for hydration (FFM D+W ) was investigated in three independent samples (AZ, IL, CA). Subjects included 75 males and 75 females ranging in age from 18 to 32 years. Whole‐body resistive index (WBRI) computed as height 2 /resistance was highly correlated to FFM Db , FFM TBW , and FFM D+W (r = 0.97, 0.95, and 0.97, respectively). Multiple regression analysis was employed to develop prediction equations for FFM Db , FFM TBW , and FFM D+W . In each prediction equation, WBRI was the single best predictor. Accounting for sex and variation in body weight significantly improved the prediction equations, by increasing the R 2 s to 0.95, 0.94, and 0.96 and decreasing the SEEs to 2.6, 3.2, and 2.5 kg, for FFM Db , FFM TBW , and FFM D+W , respectively. Similarity of the SEEs between methods (less than 1.0 kg difference) suggests consistency in the precision of WBRI estimates for body composition.