To the Editor:

Because of limitations in treatment resources, patients with anorexia nervosa are often asked to gain weight in intensive outpatient programs rather than in traditional inpatient treatment settings. Little is known about the efficacy of intensive outpatient treatment for weight gain in patients with anorexia nervosa.

Using a retrospective chart review of patients with anorexia nervosa, we matched 23 inpatients and 23 patients in intensive outpatient treatment by diagnosis and age, comparing admission and discharge weights, lengths of stay, and rates of weight gain. The inpatient and outpatient groups did not differ significantly on age, age at onset of eating disorder, or duration of illness. The inpatient group weighed significantly less at admission than the outpatient group (mean percent of ideal body weight=71%, SD=9, versus mean=80%, SD=6) (t=–4.0, df=44, p<0.0001). However, the inpatients gained 15% of their ideal body weight during 46 days (SD=27) of hospitalization, at a rate of 0.3% of ideal body weight per day. By comparison, the patients in intensive outpatient treatment gained only 1.4% of ideal body weight during 69 days (SD=45) of treatment, at a rate of 0.01% of ideal body weight per day (difference in weight gain: t=5.9, df=44, p<0.0001).

There was a linear relationship between weight gain and length of stay for the inpatients (r=0.77, p=0.0001) but not for the outpatients (r=–0.07, n.s.). In fact, only seven of the 23 outpatients showed a gain of more than 5% of ideal body weight during treatment. The remaining 16 outpatients showed little weight gain or even lost weight during treatment. Moreover, the outpatients who successfully gained weight all did so at a lower rate than the inpatient group with the lowest percentage weight gain. The subgroups of outpatients and inpatients who gained weight did not differ significantly from the outpatients and inpatients who did not gain weight on any pretreatment variable.

In summary, subjects gained significantly more weight at a faster rate during inpatient treatment than during intensive outpatient treatment. Intensive outpatient treatment was less effective in promoting weight gain and thus may be more expensive over time. It is important to note that the inpatients were supervised during 35 meals a week, whereas the outpatients were supervised for three to 13 meals a week. It is well known that people with anorexia nervosa are resistant to eating a normal number of calories, not to mention gaining weight. Underweight patients with eating disorders tend to eat little during unsupervised meals; this is likely to account for the large differences in weight gain between the outpatient and inpatient groups.

The patients receiving intensive outpatient treatment who gained weight did so at a rate similar to that reported by the Toronto Hospital partial-hospitalization eating disorder programs (1, 2). We are not aware of other studies comparing weight gain in inpatients and outpatients with anorexia nervosa in intensive treatment. However, a number of clinical centers have informally reported similar frustration in trying to promote weight gain in intensive outpatient programs, as reported on an e-mail chat line of the Academy for Eating Disorders.

Further research on the efficacy of eating disorder treatment programs in restoring weight in patients with anorexia nervosa is greatly needed. On the basis of our findings, such studies are likely to show that, in the long run, inpatient treatment is more cost-effective than intensive outpatient treatment for restoring weight in underweight patients with anorexia nervosa.