The Impact of Weight Concern in Anorexia Nervosa: How Much From 'Weight' and How Much From 'Concern'?

Objective: In the CBT model of anorexia nervosa, emaciation is assumed to occur because individuals over-value their weight and shape. However, current BMI (for adolescents, BMI z-score) may be relevant to psychopathology beyond its relation with weight concern. We explored the relations between BMI/z-BMI and attempts to change one's eating and/or weight (restraint and eating concern) before and after controlling for weight concern among individuals with AN or atypical AN (AAN).

Method: Participants were 1666 female residential patients with AN or AAN. For those below age 21, we examined the relations between z-BMI and EDE-Q Restraint and Eating Concern when Weight Concern was and was not controlled. For adults, we conducted the same analyses using BMI.

Results: BMI and z-BMI were positively related to weight concern, restraint, and eating concern. When controlling for weight concern, the positive relationships between z-BMI and both restraint and eating concern became significant negative relationships. This pattern also emerged among adults, though the negative relationship between BMI and restraint did not reach significance.

Conclusions: In AN-spectrum disorders, (1) BMI/z-BMI was related to weight/eating concerns despite substantial weight loss and (2) when weight concern was controlled, these relationships between BMI/z-BMI and restraint/eating concerns were largely reversed.