Objective. To analyze the diagnostic value of fear of weight gain (obesity) criterion in anorexia nervosa (AN). Material and methods. Authors examined 30 patients with significant weight loss due to self-restriction of food intake. The patients were stratified into the group (n=15) that met ICD-10 criteria of AN (restrictive variant) and the group with somatoform dysfunction of the autonomic nervous system of the gastrointestinal tract. Authors compared these groups and presented a description of two cases. Results. The patients of the second group met 3 of 4 AN criteria and would be formally diagnosed with atypical AN but they had not the fear of weight gain. Moreover, the patients of this group significantly differed by several clinical parameters and responses to treatment. In diagnostic view, the most important is the presence of the dysmorphophobia/dysmorphomania syndrome in patients with AN and hypochondriac syndrome in the patients with somatoform dysfunction. Conclusion. The diagnostic criteria of eating disorders should be revised. However, «fear of weight gain», to our opinion, should be considered as a necessary criterion of AN.