Fat is an electrical insulator, whereas lean tissue, being a solution of electrolytes, will conduct an electric current. If electrodes are attached to the hand and foot, and an extremely small alternating electric current (typically 80 ^A at 50 MHz) is passed between them, measurement of the fall in voltage permits calculation of the conductivity of the body. The percentage of fat and lean tissue can be calculated from equations based on a series of studies in which this technique has been calibrated against direct determination of density (section 126.96.36.199).
Measurements of either total body electrical conductivity (TOBEC) or bioelectrical impedance (BIE) are used mainly in research, but as the equipment becomes more widely available these methods will become the methods of preference for routine estimation of body fat.
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