Anorexia nervosa in partial remission with comorbid OCD: orthorexic cognition as a potential maintaining factor — a case report

Anorexia nervosa (AN) is frequently accompanied by compulsive hyperactivity, obsessive–compulsive traits, and rigid cognitive styles. Orthorexia nervosa (ON), characterized by an excessive preoccupation with healthy or “pure” eating, has been described as a related but conceptually distinct pattern of restrictive eating psychopathology. Differentiating AN, ON, and obsessive–compulsive disorder (OCD) remains clinically challenging, particularly when features co-occur. We report the case of a woman in her twenties with long-standing AN who maintained persistent underweight (BMI 13–14 kg/m²) despite a daily caloric intake of 2,000–2,500 kcal. Her presentation was notable for marked compulsive overactivity (>400 minutes/day), rigid dietary rules focused on purity, avoidance of additives and oils, and significant anxiety related to perceived dietary “contamination”. Psychometric assessments showed moderate to severe OCD (Y-BOCS 23), pronounced orthorexic features (ORTO-15 score 39; Japanese TOS score 17), and clinically relevant eating pathology (EAT-26 score 41). Despite adequate caloric intake, weight restoration during the acute phase was limited by excessive energy expenditure driven by intrusive compulsive urges. However, following comprehensive multimodal treatment, the patient has been able to maintain a stable daily life, characterized by improved regulation of physical activity, more flexible and nutritionally balanced eating patterns, and sustained engagement in community-based vocational activities. This case demonstrates the diagnostic and therapeutic complexity that arises when AN, ON, and OCD-like traits converge. The patient’s ego-syntonic commitment to dietary purity, combined with intrusive urges to exercise, produced a self-reinforcing cycle of restrictive eating and compulsive behavior. Social media exposure also appeared to amplify orthorexic beliefs, consistent with prior findings linking digital health content to ON symptom severity. Clinicians should assess orthorexic cognitions and compulsive exercise in patients with persistent underweight despite adequate intake. Integrated interventions targeting cognitive rigidity, health-related obsessions, and maladaptive activity patterns are essential for effective treatment.