Relapse in AN: Percent Body Fat is a Risk Factor

After weight is restored, patients with low body fat are at greater risk.

As many as half of patients with anorexia nervosa (AN) will relapse at least once, and these patients are at greatest risk for additional relapse during the first year after hospitalization. Identifying factors that place patients at greater-than-normal risk may help lower the recidivism rate.

Lindsay P. Bodell and Laurel E.S. Mayer MD, of New York State Psychiatric Institute, New York City, have targeted what they feel is an important relapse risk factor for AN patients, the percentage of body weight after weight restoration. In an earlier study, the authors had identified the percentage of body fat as a factor that increased the risk of relapse among 26 AN patients (Am J Psychiatry 2007; 164:970). In a newer study reported in the International Journal of Eating Disorders (2010. [Epub ahead of print]), the researchers found that a lower percentage of adipose tissue after short-term weight normalization was associated with a poorer outcome during the first year after inpatient treatment.

In the current study, 22 women between the ages of 18 to 45 years with AN were assessed for changes in body composition and body fat distribution in the year following inpatient treatment on an eating disorders unit. All the women met all the criteria for AN as listed in the Diagnostic and Statistical Manual of Mental Disorders-IV-TR, except for the amenorrhea criterion. Their treatment on the unit consisted of a structured behavioral program aimed at normalizing weight and eating behaviors. If they did not gain 1 lb of weight per week with the prescribed program of three meals and one snack per day, additional calories were added in the form of a liquid nutritional supplement (Ensure™ or Ensure Plus™). One criterion for discharge from the unit was restoration of weight to at least 90% of ideal body weight (IBW) as defined by Metropolitan Life actuarial tables. Body composition was assessed in participants after they maintained 90% of IBW for 2 to 4 weeks.

On the morning of testing, weight was measured to the nearest ¼ lb with a calibrated physician’s beam balance scale and total body magnetic resonance imaging was performed. Images were analyzed for body composition, and percent adipose tissue was calculated as total adipose tissue divided by body weight x 100, and this calculation was used as a proxy for percent body fat.

After the inpatient program ended, patients were discharged to treatment in the community. Monthly phone calls by research staff helped follow the patients to obtain information about eating disorder symptoms and weight; every 3 months the participants had in-person evaluations.

More than half had a ‘poor’ outcome

Follow-up information was available for 21 of the 22 patients (one did not return phone calls and was lost to follow-up). Nineteen of the 21 participants completed enough information to determine Morgan-Russell criteria. Of the 21 participants, the outcome for 10 was categorized as “full,” “good,” or “fair,” but for 11 others, it was “poor.” As the authors had expected, there was a significant difference in body mass index, or BMI (mg/k2) between the full, good, or fair results groups and the poor outcome group: 20.8 kg/m2 vs.16.2 kg/m2, respectively.

At the time of initial testing, age, duration of illness, diagnostic subtype and BMI were not significantly different between the women with good, full, or fair outcome and the group with a poor outcome. At the end of one year, however, percent body fat was significantly lower in those with poor outcomes (22% body fat) compared to the three other groups (27% body fat).

According to the authors, the study results suggest that lower percent body fat in recently weight-restored women with AN may be a risk factor for relapse, and normalization of body fat levels may be an important element in long-term recovery from AN. Analyzing body composition may help identify patients at risk for relapse.