In the early twentieth century, Donini et al. (2004) and Cartwright (2004) independently published the findings and/or observations about orthorexia nervosa for the first time. Over the last 20 years, several studies have been conducted in different countries to investigate the phenomenon of orthorexia nervosa. Nonetheless, an up-to-date overview of the clinical description of orthorexia nervosa (especially clinical diagnosis) remains challenging. To date, orthorexia nervosa as a unique diagnostic category or a mental disorder (included among the eating disorders or considered as an obsessive-compulsive disorder) lacks recognition in the DSM 5 (or DMS-5-TR) and the ICD-11. This is mainly because not enough studies have been published on the condition to distinguish it from other disorders.