Pre-occupation with the idea that one’s body is not sufficiently lean and muscular. Characteristic associated behaviours include long hours of lifting weights and excessive attention to diet. The pre-occupation is manifested by at least two of the following four criteria:

(1) The individual frequently gives up important social, occupational or recreational activities because of a compulsive need to maintain his or her workout and diet schedule.
(2) The individual avoids situations where his or her body is exposed to others, or endures such situations only with marked distress or intense anxiety.
(3) The pre-occupation about the inadequacy of body size or musculature causes clinically significant distress or impairment in social, occupational or other important areas of functioning.
(4) The individual continues to work out, diet or use performance-enhancing substances despite knowledge of adverse physical or psychological consequences.

The primary focus of the pre-occupation and behaviours is on being small or inadequately muscular, as distinguished from fear of being fat as in anorexia nervosa, or a primary pre-occupation only with other aspects of appearance as in other forms of body dysmorphic disorder.