Bio-impedance analysis for estimation of total body potassium,total body water,and fat-free mass in white,black, and Asian adults

Bio-impedance analysis (BIA) measurements have been used to predict components of body composition. Their validation is required for populations varying in race, sex, and age. In 371 Whites, 182 Blacks and 225 Asians, single-frequency BIA at 50 kHz (RJL-100) resistance and reactance measurements were correlated with same-day measurements of total body water (TBW) by THO dilution, total body potassium (TBK) by whole body ⁴⁰K counting, and fat-free mass (FFM) by dual-photon absorptiometry. BIA correlation coefficients with TBW, TBK, FFM, and fat varied by sex and race for all measured body composition components. The highest correlation was for FFM, and the lowest was for fat mass. Prediction equations were further improved by including age, stature, and weight for each of the study cohorts. The SEE for predictions were in the ranges of 5–6, 6–8, and 7–10% of measured FFM, TBW, and TBK, respectively. BIA was effective in predicting body composition when subjects are specified by age, sex, stature, weight, and race for subjects from 18 to 94 years of age. © 1995 Wiley-Liss, Inc.