The reliability of bioelectrical impedance analysis for measuring changes in the body composition of patients with anorexia nervosa

Objective: To determine whether bioelectrical impedance analysis (BIA) is a valid measure of change in body fat in anorexia nervosa (AN) patients during refeeding, as compared to skinfold calipers (SF). Methods: Prospective cohort study with measures of BIA and SF performed once a month for 3 months on patients meeting the DSM-III-R criteria for AN who received treatment from the Eating Disorders Clinic of a university teaching hospital as inpatients or outpatients. Results: Twenty patients completed the study. Comparison of the two methods by the Pearson correlation coefficient showed a weak negative correlation of r = -.305. Analysis by a graphical method confirmed the poor agreement that exists between the two methods. Discussion: The inability of BIA to detect changes in body composition due to altered hydration, and to accurately assess the distribution of water between intracellular and extracellular compartments, limits its clinical usefulness in AN. It appears that SF measurements are preferable to BIA as a measure of body fat change in patients with AN