Yes, men can absolutely be affected by their body image. Body image issues are typically associated with eating disorders, such as anorexia nervosa and bulimia. These disorders can affect either gender, but are more common in women. Men who suffer from a body image issue typically perceive themselves as smaller (in terms of muscle size) than they actually are. This is one form of dysmorphophobia, also known as body dysmorphic disorder. Men suffering from this disorder are obsessed with achieving the 'perfect' body. They are constantly judging and critiquing themselves in the mirror. These individuals chronically over-exercise, causing further mental and physical distress.
Body image issues are dangerous because of their drastic affects on behavior. People become imprisoned in their own minds because what they perceive as real doesn't match up with reality. It is often difficult for individuals suffering from body image issues to conquer these demons without psychological help.