The effects of lipid location on non-invasive estimates of body composition using EM-SCAN technology.

We evaluated the effect of lipid location on body-composition estimation accuracy using electromagnetic scanning (EM-SCAN), a non-invasive [total body electrical conductivity (TOBEC)] method. Molds were constructed that simulated a 'general' small mammal, either 93% lean/7% lipid (control) or 82% lean/18% lipid (lipid-location groups). In the 18% lipid molds, we varied the location of the fat; simulating all the fat in the head, tail or midsection or simulating homogenous distribution. Comparisons were made between the EM-SCAN output of each lipid-location group, and multiple-regression techniques were performed to derive body-composition estimation equations for both lipid mass (M(L)) and fat-free mass (M(FF)). Device output varied significantly for all lipid-location groups even though all groups contained 18% body fat, showing a lipid-location effect on device output. Calibration equations derived for each lipid-location condition estimated both M(L) and M(FF) accurately, but an independent equation was required for each lipid-location condition. In situations where species significantly vary body fat content and location, for example during hibernation or reproductive periods, we suggest deriving a calibration equation that is more representative of the actual body composition to improve M(L) and M(FF) estimation accuracy using non-invasive EM-SCAN methods.