Maintaining a Healthy BMI after Recovery from AN

A focus on the health benefits of food,
aided by genetics and biology

After recovering from anorexia nervosa (AN), women tend to maintain lower body mass indexes (BMIs, kg/m²) than do women in the general population. In a pilot study, Jocilyn E. Dellava, PhD, and colleagues at the University of North Carolina at Chapel Hill and Virginia Commonwealth University, Richmond, recruited a small group of women between 18 and 65 years of age who had no current medical conditions that could influence weight, diet, or activity levels (Int J Eat Disord 2011; 44:376).

All women in the recovered group met lifetime diagnostic criteria for AN, including amenorrhea, and had not met diagnostic criteria for any eating disorders during the 3 years before the study began. Complete data were compiled for 15 women recovered from AN and from 18 control women.

The researchers used the Structured Clinical Interview of DSM-IV Axis 1 Disorders–Patient Edition (SCID-I/P) to establish the presence or absence of current and lifetime eating disorders. Next, current height and weight were measured, and these were used to establish the subject’s current BMI. The Food Choice Questionnaire was used to determine factors that had an impact on the participants’ food choices. The women were also asked to wear an Actigraph, activity monitor for 3 weekdays and one weekend day. The epoch length was set to 1 minute and 60 consecutive zero counts was considered an indication that the monitor was not being worn. Finally, the Reasons for Exercise Inventory (REI) was used to record the reasons for exercising. The REI uses 24 questions and subscales to assess weight control, fitness, mood, attractiveness, health, enjoyment, and tone.

After recovery, a glimpse of new behaviors

The results of this pilot study offer a first glimpse into eating and activity behaviors of persons who have recovered from AN. Age was not significantly different between recovered and control women (35.2 years vs. 28.9 years, respectively). The women had been recovered for a mean of 12.9 years (range: 3.0 years to 32.0 years). Overall, energy intake, macronutrient composition of the diet, and the level of activity did not differ significantly in women recovered from AN compared with women without a history of an eating disorder.

The authors reported that after recovery from AN, women with histories of AN seem to focus more on the health benefits of food more than do their peers. Women who had recovered from AN had BMIs over 2 units lower than did women without a history of an eating disorder, and a numerically lower percentage of recovered women were considered overweight or obese.

When the researchers looked at possible biological mechanisms that might be involved, they considered that women recovered from AN might have higher fat oxidation than do women without an eating disorder. Higher fat oxidation might be associated with an ability to attain and maintain lower BMIs. Another possible explanation might result from differences in uncoupling proteins. These factors are positively associated with resting metabolic rate and negatively associated with fat mass higher than expected resting metabolic rate could account for lower BMIs. Lower percent fat mass would contribute to higher resting metabolic rate and also to lower BMIs.

The authors also noted that AN may be associated with other genetic variations that influence the development of maintenance of a low BMI before, during, and after acute AN. A third possibility is that non-exercise activity thermogenesis may be higher in recovered individuals than in persons without a history of an eating disorder.

Two limitations to the study were that it involved a small number of subjects and several of the women in the control group did not provide complete information in their food journals or about their physical activity. The authors suggest that future studies further explore the biologic mechanisms and genetic variants that might contribute to lower BMIs after recovery.