Significant prevalence rates of pathological healthful eating and its extreme form, orthorexia nervosa (ON), the pathological obsession with healthy eating, have led to increased efforts to understand this phenomenon's clinical relevance. This narrative review qualitatively summarizes existing evidence on the (psycho-)pathology and consequences of ON and offers an interpretation within the frame of existing theories and models of psychiatric disease. Adding to the controversy in the field of ON, this review offers important critiques and identifies gaps in our current understanding of ON as a (distinct) mental illness.