The relation of weight suppression and body mass index to symptomatology and treatment response in anorexia nervosa

Abstract

Weight suppression, the difference between highest past weight and current weight, is a robust predictor of clinical characteristics of bulimia nervosa; however, the influence of weight suppression in anorexia nervosa (AN) has been little studied, and to our knowledge, no study to date has investigated the ways in which the relevance of weight suppression in AN may depend upon an individual's current body mass index (BMI). The present study investigated weight suppression, BMI, and their interaction as cross-sectional and prospective predictors of psychological symptoms and weight in AN. Women with AN completed depression (Beck Depression Inventory-II) and eating disorder symptomatology measures (Eating Disorder Examination Questionnaire and Eating Disorders Inventory-3) at residential treatment admission (N = 350) and discharge (N = 238). Weight suppression and BMI were weakly correlated (r = -.22). At admission, BMI was positively correlated with all symptom measures except Restraint and Depression scores. Weight suppression was also independently positively correlated with all measures except Weight Concern and Body Dissatisfaction subscale scores. In analyses examining discharge scores (including admission values as covariates), the admission weight suppression × BMI interaction consistently predicted posttreatment psychopathology. Controlling for weight gain in treatment and age, higher admission weight suppression predicted lower discharge scores (less symptom endorsement) among those with lower BMIs; among those with higher BMIs, higher weight suppression predicted higher discharge scores. These results are the first to our knowledge to demonstrate that absolute and relative weight status are joint indicators of AN severity and prognosis. These findings may have major implications for conceptualization and treatment of AN.

Figure 1

Conceptual representation of the relation between varying levels of weight suppression and current and highest adult body mass index (BMI; kg/m²) among patients with anorexia nervosa. The vertical bars represent weight suppression (WS), the difference between highest BMI at adult height (diamonds) and current BMI (circles).

Figure 2

Relations among admission weight suppression, admission BMI, and EDE-Q Global scores at discharge. EDE-Q Global subscale score values graphed represent discharge values controlling for baseline values, age, and weight change over treatment, with all participants included. The relationship between weight suppression and EDE-Q Global score was significantly moderated by BMI (p = .007). The pattern of results was similar using only the confirmed-diagnosis sample, and for all statistically significant EDE-Q, EDI-3 and BDI-II outcome measures.

Figure 3

Relations among admission weight suppression, admission BMI, and BMI at discharge. BMI values graphed represent discharge values controlling for baseline values and age, with all participants included. Weight suppression at admission was consistently positively associated with absolute weight status at discharge, but admission BMI moderated this relation (p =.006), which was strongest among those with lower BMIs at admission. The pattern of results was similar including only the confirmed-diagnosis sample.