The predictive value of body mass index for the weight evolution in anorexia nervosa

Low body weight is considered to be an important risk factor for poor outcome in anorexia nervosa (AN).

To study the relationship between body mass index (BMI) at the beginning of treatment and at follow-up. A BMI of 13 kg/m2 at admission was hypothesized as cut-off point for better versus worse evolution of weight after treatment.

The BMI of 232 female AN inpatients was calculated at admission and after 6 months and 1 year.

An overall low correlation between BMI at admission and at 6 months (r = 0.27) and 1 year (r = 0.26) follow-up was found. A BMI value of 15 kg/m2 at admission was revealed as the best cut-off point for making predictions.

Patients with an admission BMI below 15 kg/m2 have a significantly greater chance to develop a lower BMI value at follow-up than those with a higher BMI.