Body composition and menstrual status in adults with a history of anorexia nervosa—at what fat percentage is the menstrual cycle restored?

Objective To study the association between body composition measures and menstrual status in a large sample of adult patients with a history of anorexia nervosa and to calculate the predicted probability of resumption of menstrual function. Furthermore, to establish whether fat percentage is superior to body mass index in predicting the resumption of menses. Method One hundred and thirteen adult women with a history of anorexia nervosa underwent a dual energy X‐ray absorptiometry (DXA) scan and completed questionnaires regarding medication prescription and menstrual function. Results Fifty percent of patients were expected to resume their menstrual function at a body mass index of 19 kg m−2 or a fat percentage of 23%. Twenty‐five percent of patients were expected to resume their menstrual function at body mass index 14 kg m−2 or fat percentage 11%. Fat percentage and body mass index were equally capable of predicting the resumption of menses. Discussion Fat percentage and body mass index were positive predictors of the resumption of menses, however, body composition measured by dual energy X‐ray absorptiometry was not superior to body mass index in predicting menstrual recovery, which is of great clinical relevance as body mass index is easier and cheaper to obtain. Body composition measures only account for one of numerous factors involved in the resumption of menses. Regression models based on our data had a R2 value of 0.14, indicating that only 14% of the variation in menstrual recovery could be explained by the variables included.