Explain the Bioelectrical impedance Analysis (BIA)?

The difficulty of measuring total body water (TBW) by Isotope Dilution Method led to the search of Bioelectrical Impedance Analysis (BIA). The technique is based on the assumption that tissues that are high in water content will conduct electrical currents with less resistance than those with little water. Adipose tissue contains little water and is a relatively poor conductor of electricity; therefore, fat will impede the flow of electrical current. Fat-free tissue is a better conductor of an electrical current (contains water and electrolytes) than fat tissue. An electric current is. Passed through the body and, with equations, FFM and fat can be calculated. The resistance to current flow is inversely related to FFM. BIA and its accuracy is dependent on apparatus and valid choice of prediction equation used.

The BIA technique is considered to be a secondary measurement because it just be calibrated using a reference technique such as deuterium dilution for TBW. The increasing popularity of this technology can be attributed, in part, to the low cost of the instruments, their simplicity of operation and the high reproducibility obtained for the individual.