Bioelectrical impedance analysis: the electronic skin-fold caliper?

A novel method utilising both tetrapolar and bipolar impedance analysis was developed for the measurement of the impedance of skin and underlying subcutaneous tissue. Impedance and skin-fold thickness were measured at four sites (biceps, triceps, subscapular and suprailiac) conventionally used for measurement of skin-folds and estimation of total body fat. Impedance was highly and significantly correlated (r=0.80 to 0.94) with skin-folds at three sites (biceps, subscapular, suprailiac) and more weakly (r=0.57) at the triceps. Both inter- and intra-observer reliability of measurement of impedance was higher than for skin-folds. The method has potential as a simple but more reliable method for the estimation of skin-folds but awaits validation against an accepted reference method such as ultra-sound or MRI.