VALIDITY OF BEOELECTRICAL IMPEDANCE MEASUREMENT FOR DETERMINING CHANGES IN HUMAN BODY COMPOSITION DUReNG WE [ GHT REDUCT [ ON

A study was conducted to investigate the validity of bioelectrical impedance measurement (BIM> for determining changes in body composition during treatment of obesity with an exercise and diet regimen. Eleven obese women, aged 38n"57 yr (44± 6.0 yr), participated in a weight reduction study. Before and after the weight reduction period, body composition was rneasurecl by the deuterium oxide (D,O> di!ution and BIM methods. For both methods, the correlation coe'encients were of the same order of magnitude under both preand postregimen conditions. Mean weight reduction was 3.59± 1.518kg and loss of total body fat was estimated to be 4.8± 1.72 kg by the D20 method and 2.5± 1.14kg by the BIM method. Thus the BIM method underestimatecl the change in body fat compared with the D20 method. Changes in resistance (R)and height squared divkled by R were not significant at the p>O,05 level. Hewever, the mean change in fat-free mass (FFM) found by the D,O method was significantly greater than that found by the BIM method. Furthermore, there was no significant correlation between the changes in FFM estimated by the D20 and BIM rnethods. These results show that after weight reduction the BIM method overestimates body composition. It is conclucled that the BIM method is mota yalidapproach for measuring the small changes in body composition that occur during treatment of obesity. (Jpn. J. I]hys. Fitness Sports Med. 1992, 41:576N585) key words : Bioelectrical impedance, Total body water, Weight reduction