Assessment of body composition in adolescent subjects with anorexia nervosa by bioimpedance.

Our main goal was to test various impedance methods for measuring body composition in adolescents with anorexia nervosa (AN) during refeeding therapy. A specific objective was to compare the information provided by a foot-to-foot impedancemeter (FFI) with that supplied by a medical multifrequency impedancemeter and by dual X-ray absorptiometry (DXA). We have monitored 13 young AN subjects and 17 healthy controls of a similar age group using a Xitron 4200 multifrequency impedancemeter measuring extracellular (ECW) and total body water (TBW) volumes and a Tefal Bodymaster FFI measuring weight (W), fat-free-mass (FFM) and body fat mass (FM). This Tefal device has been modified to measure in addition ECW and TBW resistances permitting to calculate ECW and TBW volumes using appropriate algorithms. In addition FFM and FM were measured by DXA on AN subjects. FFM measured by the FFI and the Xitron in AN subjects were found to be respectively 7.8% and 4.5% lower than FFM measured by DXA. TBW measured by FFI was not significantly different from that measured by Xitron in AN subjects and in controls. ECW measured by the FFI was not significantly different from that measured by Xitron in controls, but was in AN subjects. The body cell mass to (height)2 ratio was found to be significantly different between AN subjects and controls. The modified FFI was found to be simpler and quicker to use than the Xitron, while giving similar information.