Outpatient therapy for adult anorexia nervosa : early weight gain trajectories and outcome

Objective: The purpose of the study was to identify latent classes of trajectory of change in body mass index (BMI) between the initial and thirteenth session of outpatient treatment for adult anorexia nervosa and identify the association with outcome. Method: Participants (n = 120) were randomised to one of three outpatient therapies. Results: Four latent classes were identified; two classes (higher, rapid and higher, moderate) had BMI > 17 kg/m2 at initial assessment, and both gained significantly more weight over the 13 sessions compared to the other two classes. The third and fourth classes (middle, stable and low, stable) had an initial BMI of 16.44 and 15.31, respectively, and neither gained weight over the first 13 sessions. Compared to the other three classes, the higher, rapid class (N = 19, 16%) showed a significantly greater BMI increase over the first 13 sessions of therapy and a significantly higher rate of remission at end of treatment and 12-month follow-up (18–22 months post-randomisation). Conclusions: The group with the greatest early weight gain had significantly higher levels of remission. Higher BMI at baseline without substantial early weight gain was insufficient to produce higher levels of remission than those with lower weight at baseline