muscle dysmorphia

noun

: pathological preoccupation with the perceived smallness or weakness of one's body and musculature often leading to excessive exercise (such as bodybuilding), steroid abuse, or eating disorders

A typical sufferer of muscle dysmorphia is a man who weighs himself several times a day, compulsively examines himself in the mirror, and fails at relationships because he is unwilling to devote time or energy to others …

—Eileen Smith, USA Today

… researchers from Boston's McLean Hospital compared 30 normal weightlifters to 24 men with muscle dysmorphia—a disorder defined by a pathological preoccupation with increasing muscularity.

—Kelly McCarthy, Psychology Today

called also bigorexia, reverse anorexia

see body dysmorphic disorder