CAN BIOELECTRICAL-IMPEDANCE IMPROVE THE PREDICTION OF BODY-FAT IN PATIENTS WITH EATING DISORDERS

Prediction equations for percentage body fat have been derived for a g roup of 93 female patients being treated for eating disorders, using f at measured by dual-energy X-ray absorptiometry (DXA) as the reference method. Separate bioelectrical impedance analysis (BIA) prediction eq uations were derived for patients with a body mass index above and bel ow 16 kg/m2. This provided an improvement compared with the equations supplied by the manufacturer. The standard error of the estimate (SEE) for the entire group was 3.2% (r = 0.922). However, an alternative pr ediction equation based on anthropometry alone gave an SEE of 4.2% (r = 0.861). The ability of BIA and anthropometry alone to measure change s in percentage fat was assessed in a separate group of 24 females dur ing treatment for eating disorders. The SEEs using the BIA and anthrop ometry prediction equations were 2.6% (r = 0.931) and 2.7% (r = 0.901) respectively. We conclude that in patients with eating disorders BIA does not provide any significant improvement over simple anthropometry prediction equations for the assessment of percentage fat or its chan ges. The apparently reasonable agreement between fat predicted by BIA and that measured by DXA is largely due to the inclusion of body habit us parameters in the BIA prediction equations.