Background:
Inpatient treatment successfully increases body weight and decreases eating disorder and associated symptoms in patients with anorexia nervosa (AN). However, relapse rates are high, particularly within the first year after discharge.

Methods:
We examined treatment outcome one year after discharge in adults with AN (N = 80, 2 males; BMI at admission: M = 13.2 kg/m2, SD = 1.79) who received treatment in a specialized inpatient unit for AN patients with severe underweight (body mass index < 15 kg/m2) and/or excessive purging or exercising.

Results:
From admission to discharge, body weight and self-reported life satisfaction significantly increased and self-reported eating disorder symptoms, depressive symptoms, and compulsive exercise significantly decreased. From discharge to follow up, life satisfaction and body weight decreased, and eating disorder symptoms, depressive symptoms, and compulsive exercise increased, although 87% of patients indicated to have received some kind of eating disorder treatment in the past six months. At follow up, the majority of patients indicated that they regularly ate three meals per day in the past week, including consumption of high-calorie, formerly forbidden foods. However, only a minority of patients indicated that they adhered to the hospital’s guidelines on portion sizes. Patients’ self-reported desired body weight at follow up was significantly higher than their current body weight.

Conclusions:
While inpatient treatment results in substantial improvements that are partially maintained after discharge, severe and extreme cases of AN require more long-lasting, alternating treatment approaches (e.g., interval treatment) to ensure long-term recovery.