gms | German Medical Science

Background: Patients suffering from anorexia nervosa (AN) have an extraordinary strong ability to limit food intake. In contrast, patients suffering from bulimia nervosa are characterized by frequent disruptions in inhibitory control leading to eating attacks. Thus, deficits in terms of dysfunctional approach vs. avoidance behaviors towards food are evident in eating disorders.

Methods: In order to investigate approach and avoidance in AN using food stimuli, we applied an approach-avoidance task (AAT), in which patients either approached (“pull”) or avoided (“push”) high vs. low calorie food pictures based solely on the presented picture format (landscape vs. portrait). By doing so, the hypothesis was tested that -in opposition to healthy controls displaying an approach bias towards high calorie food cues- patients suffering from AN would show a differential response with regard to high vs. low calorie stimuli, in terms of an avoidance bias (measured as different response times) towards high calorie food pictures. N = 41 AN patients and n = 42 healthy controls were included. Explicit ratings of food cues were also carried out in patients and controls.

Results: We found a significant interaction „group“ x „direction“ of motion (p = 0.03), indicating that the groups had significantly different response times (RTs) with regard to the “direction” of motion in the AAT. Subsequently, rm-ANOVAs performed for each of the two groups separately, showed a main effect for „direction“ of motion in controls (p = 0.02). There was no main effect for „direction“ seen in the group of patients with AN (p = 0.40). The two groups did not differ in their RTs with regard to „push“ (p = 0.27). However, RTs with regard to „pull“ were significantly different between the groups (p = 0.04).

Conclusions: Healthy controls show a clear approach bias, expressed by significantly faster RTs for “pull” compared to “push”, independent of “calorie” content of the food stimuli. This approach bias is absent in the group of patients with AN. This is indicative of a global loss of incentive value of food for patients with AN and explains their ability to rigorously limit food intake (irrespective of calorie category). In view of the results presented here, implicit trainings aimed at attenuating the inhibitory control in patients with AN are asked for.