Fat-free mass qualitative assessment with bioelectric impedance analysis (BIA).

Body composition studies, when based on two-compartment volumetric estimates, can hardly assess nutritional states. Phase-sensitive impedance analysis can be used to reflect directly the proportions between intra- and extracellular spaces (ECM/BCM), which is one of the most sensitive indexes of malnutrition. Resistance and reactance values actually measured with BIA are referred to as the series RC model; however, due to the morphology of the FFM, which is composed of cells surrounded by interstitial fluids, in reality this should be modeled as a parallel RC circuit. A nomogram developed with series-to-parallel transformations of resistance and reactance measured with commercial BIA on controls and patients shows interesting gender and disease sensitivity and specificity.