An evaluation of the use of total body electrical conductivity for the estimation of body composition in adult rats: effect of dietary obesity and adrenalectomy.

Total body electrical conductance (TOBEC) has been recommended for serial measurements of body composition in animals and humans. This study examined the accuracy of the TOBEC technique in predicting body composition of a population of adult male rats that had undergone seven different treatments, including adrenalectomy and blocking of glucocorticoid receptors, in the study of the etiology of obesity. The predicted body composition values of the animals (n = 57, body weight 550 +/- 8 g) obtained by using the manufacturer's and Baer's equations were compared to the actual body composition obtained by direct carcass analysis. Both equations underestimated lean body mass and reciprocally overestimated body fat (manufacturer's 103 +/- 4 g, Baer's 55 +/- 3 g). A new prediction equation was developed based on the conductivity index and the actual lean body mass. This revised equation was able to accurately estimate the lean body mass of the animals used in the same experiment but over-estimated lean body mass of larger animals (n = 10, wt. 647 +/- 13 g). Conclusions based on multiple comparisons (Duncan's) of predicted and actual values resulted in different effects of treatments on body composition. To improve accuracy and reliability of the TOBEC technique, a prediction equation should be developed from the same population as the studied population, and experimental group sizes used for examining treatment effects should be relatively large.