**3.7. Eating disorder**

Patients with eating disorders (EDs), similar to OCD, experience intrusive thoughts that contribute to maintenance of dysfunctional behaviors. Intrusive thoughts in ED typically center on food, diet, physical exercise, and appearance [31]. These intrusions trigger negative affect, which leads to engagement in behaviors to alleviate discomfort such as checking weight, compulsive exercise, binge eating, purging, or restricting food intake. Thus, both ED and OCD involve intrusive thoughts related to feared negative outcomes, which are linked to compensatory behaviors intended to reduce emotional distress [31]. OCD can present similarly to ED (for example, severe weight loss from contamination-focused OCD due to fears that food is dirty); eating only certain foods that are perceived to keep in good health for those with health-related OCD. Also the reverse can be true where patients with ED may appear to be OCD; for example, avoid having oils around due to fear of contamination of the food with fats; counting the number of bites of a piece of food; cutting the food into a certain number of pieces, etc. Studies that have assessed frequency of obsessions and compulsions in OCD and ED (particularly anorexia nervosa) patients have found symmetry obsessions and ordering compulsions to be most common for ED, while OCD patients tend to have more variety of symptoms [32].
