WHY BIOELECTRICAL-IMPEDANCE ANALYSIS SHOULD BE USED FOR ESTIMATING ADIPOSITY

The whole-body bioelectrical impedance analysis (BIA) approach for est imating adiposity and body fat is based on empirical relations establi shed by many investigators. Properly used, this noninvasive body-compo sition assessment approach can quickly, easily, and relatively inexpen sively provide accurate and reliable estimates of fat-free mass (FFM) and total body water (TBW) in healthy populations. The estimated FFM o r TBW values are used to calculate absolute and relative body fat amou nts. When different investigators follow the same standard BIA procedu res and use the same population and criterion method, similar predicti on equations and relatively small prediction errors have been reported for measurement of FFM and TBW (SEE: 1.7-3.0 for FFM and 0.23-1.5 kg for TBW). The BIA approach is most appropriate for estimating adiposit y of groups in epidemiologic and field studies but has limited accurac y for estimating body composition in individuals. When used as a simpl e index (stature(2)/resistance), BIA is more sensitive and specific fo r grading average adiposity in groups than some other anthropometric i ndexes such as the body mass index. Prediction equations based on BIA have been validated and cross-validated in children, youths, adults, a nd the elderly, in primarily white populations and, to a limited exten t, in Asian, black, and Native American populations.