The prediction of basal metabolic rate in female patients with anorexia nervosa.

ABSTRACT OBJECTIVE: To evaluate in female patients with anorexia nervosa the accuracy of a specific predictive formula for basal metabolic rate (BMR) already proposed in the literature and to derive a new disease-specific equation with the same purpose. DESIGN: Cross-sectional study. SUBJECTS: One-hundred and twenty adolescent girls (<18 y) and young-adult women (18-30 y) with anorexia nervosa. MEASUREMENTS: BMR was determined by indirect calorimetry or predicted according to the Schebendach formula, which was specifically derived for anorexia nervosa. RESULTS: On average the Schebendach formula performed well in the adolescent group but not in the young-adult group. The range including 95% of the predicted-measured differences was in both cases wider than 2000 kJ/day. In the young-adult patients the accuracy of the prediction was also related to age and body mass index. Weight and age (but not height or body mass index) emerged as predictors of BMR in the sample as a whole, and only weight when the two age groups were considered separately, thus leading to three different equations. The intercepts of these regression lines were very close and not significantly different from zero while their standard error of estimate was 500-550 kJ/day. CONCLUSION: The Schebendach formula is not very accurate in estimating the BMR of female anorectic patients. Moreover, in this group the relationship between BMR and weight was altered. The predictive formulas proposed by the present study have a Reasonable prediction power.