Muscle dysmorphia (MD), sometimes referred to as “reverse” or “big” anorexia (colloquially called “bigorexia”) is on the rise, and this article presents a comprehensive review on its history, highlights a few studies, provides the DSM-5 diagnostic criteria for both MD and body dysmorphic disorder (BDD), and discusses the behaviors associated with the conditions, including risk factors, comorbidities, and complications. In addition, the author provides questions to ask to ascertain whether MD may be present.