BETWEEN-LABORATORY COMPARISON OF DENSITOMETRY AND BIOELECTRICAL-IMPEDANCE MEASUREMENTS

Body composition was measured in nine healthy, normal-weight, weight-s table subjects in three different research centres. In each centre the usual procedures for the measurements were followed. It revealed that the measurement procedures in the three centres were comparable. Body composition was measured in each centre between 09.00 and 13.00 hours after a tight breakfast by densitometry (underwater weighing) and bio -electrical impedance. A single, total-body-water determination by D2O dilution was used as a reference value. Body fat determined by densit ometry was significantly tower in one centre, which, however, could be completely explained by a tower body weight, probably due to water lo ss (the subjects refrained for a longer time from food and drinks befo re the measurements in that centre) and, thus, by violation of the ass umptions of Siri's (1961) formula. Also, body impedance was slightly h igher in that centre, indicating a lower amount of body water. Mean bo dy fat from densitometry was also slightly lower in that centre compar ed with body fat determined by D2O dilution. Individual differences be tween body fat from densitometry and from total body water were relati vely large, up to 7% body fat. The relationship between fat-free mass from densitometry and bio-electrical impedance was not different betwe en the centres. It is concluded that differences in the relationship b etween body composition and bio-electrical impedance, as reported in t he literature, may be due to differences in standardization procedures and/or differences in reference population.