Prediction of lean body mass from multifrequency segmental impedance: influence of adiposity.

The aim of the study was to determine the influence of adiposity on the relationship between bioelectrical impedance (BIA) measurements of body segments and estimation of body composition by dual-energy X-ray absorptiometry (DXA). Multiple frequencies of whole body and segmental impedances were measured in 68 normal-weight and obese subjects (46 women and 22 men), mean age 37.2+/-14.8 years (range, 18-69). Total and appendicular lean body mass (LBM) assessed by DXA correlated significantly with total and segmental impedance values adjusted for stature in both obese and normal-weight subjects. Best fitting equations for the prediction of appendicular LBM from segmental impedance measurements were derived for the arm and leg with and without the inclusion of adiposity (the percentage of body fat measured by DXA) in the regression models. Best prediction was obtained at low frequency for the arm and high frequency for the leg. Adiposity appears to significantly influence the prediction of leg LBM by BIA. These preliminary observations need further validation to provide an accurate assessment of appendicular LBM assessment by BIA.