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

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).

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.

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.

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.