Body composition of anorexia nervosa patients assessed by underwater weighing and skinfold-thickness measurements before and after weight gain.

BACKGROUND Weight restoration is a crucial element in the treatment of patients with anorexia nervosa. Therefore, the validity of different methods for measuring body composition is important. OBJECTIVE We tested the concurrent validity of hydrodensitometry (underwater weighing) and anthropometry (12 skinfold thicknesses) and assessed body composition and subcutaneous fat before and after a refeeding program and a multifaceted program of therapy in a specialized inpatient unit for eating disorders. DESIGN The body composition of a large sample of anorexia nervosa patients (97 restricting type, 33 binging-purging type) was studied by using 2 methods both before and after weight gain. We applied a behavioral contract for weight restoration with a minimum weekly gain of 700 g and a maximum of 3 kg. Bland-Altman analysis of agreement, Pearson correlation analysis, t tests, and analysis of covariance were used. RESULTS There was good agreement between the results obtained by underwater weighing and by skinfold-thickness measurement (r = 0.76, P < 0.001); the results produced by the 2 methods did not differ significantly. On average, a significant weight gain (11.9 kg) was observed, composed of 6.6 kg fat and 5.3 kg fat-free mass. CONCLUSIONS Body fat estimation by skinfold-thickness equation appeared to be as accurate as underwater weighing. The refeeding program led to a significant increase in body weight, of which 55.5% was body fat. The mean ratio of fat-free mass to fat mass at the end of the treatment was 3.4:1.