Revealing motor insensitivity to food in Anorexia Nervosa as a potential mechanism contributing to calorie restriction: A mobile Approach Avoidance Task study

A change in implicit behavioural tendencies toward foods may contribute to the maintenance of calorie restriction in Anorexia Nervosa (AN). To test this hypothesis, we assessed approach-avoidance tendencies toward different categories of stimuli using a novel mobile version of the approach-avoidance task (AAT). The sample included 66 patients with restrictive AN and 84 healthy controls, all females. All participants performed the AAT in which they were required to approach or avoid stimuli (high-calorie foods, low-calorie foods, and neutral objects) by respectively pulling their phone towards themselves of pushing it away. Both the response time and the force of each movement were collected by means of the smartphone's accelerometer. The results revealed that patients with AN had a reduced tendency to approach food stimuli compared to healthy controls, who instead presented faster and stronger movements in approaching rather than avoiding foods as compared to neutral objects. This finding was particularly pronounced in patients with greater levels of malnutrition. No differences were instead observed comparing high-calorie and low-calorie foods. The observed reduction in the natural tendency to approach food stimuli is consistent with patients' eating behaviour and may contribute to the maintenance of calorie restriction, thus representing a possible target for novel therapeutic approaches.