Validation study of a total body electrical conductive (TOBEC) instrument that measures fat-free body mass

Validation of the model SA-2's (EM-SCAN, Inc.) ability to measure fat-free body mass (FFM) and indirectly predict body fat mass using total body electrical conductivity (TOBEC) methodology was investigated. To simulate changes in FFM (6.8 to 27.2 g) and fat mass (5 to 20 g), saline and oil, respectively, were injected into multiple sites of male Sprague-Dawley rats in separate trials. Two identical experiments were conducted; only the body weights differed. In Experiment 1 the rats' starting body weight averaged 171.8 +/- 3.4 g, while it averaged 214.0 +/- 2.8 g in Experiment 2. In Experiments 1 and 2, model SA-2 was used, and theoretical changes in FFM had correlations of r = 0.88 and r = 0.82, respectively. There was a tendency of the machine to consistently overpredict FFM as greater amounts of saline were injected. In Experiment 1, when oil was injected, FFM remained extremely stable, whereas in Experiment 2, it consistently overpredicted the amount of fat added in these heavier rats. Because the overpredictions in both the cases were consistent, an adjustment to the prediction equation can possibly correct these problems. Until this is done, caution must be used in interpreting data gather from the model SA-2.