The study of 200 young heterosexual men, which has been published in the Journal of Health Psychology, found that it was so common for men to worry about their muscle definition (82 per cent did) that such concerns could be considered normal.
''Clearly it is not a small sub-group of pathologically narcissistic men who experience dissatisfaction with these body parts but a substantial proportion," the Sydney Morning Herald quoted professor Marika Tiggemann, from Flinders University, as saying.
"People thought this was only a women's issue," Professor Tiggemann said.
Earlier studies had underrated men's dissatisfaction with their appearance as they assumed men would be unhappy about the same things as women: weight and body proportions.
The new study, however, has used the survey to pinpoint men's overall feelings about their body.
According to the expert, like women who risk eating disorders from extreme dieting, men's muscle concerns could lead to serious health problems, such as steroid abuse or injury.
The study found that the amount and distribution of hair on the face and body were important to men.
However, there were contradictions, such as the trend of shaving the entire head to conceal partial baldness, and the shift towards smooth male torsos in advertising, a reversal of the traditional association between male body hair and virility.
Other evidence - the arrival of men's salons and skin products and a reported increase in men undergoing cosmetic surgery - suggested male body worries were increasing, Professor Tiggemann said, and this in turn might be attributable to social change.
For girls and women - and increasingly for men - research showed that viewing pictures of idealised bodies provoked immediate feelings of dissatisfaction with their own bodies.
Professor Tiggemann said the source of men's unhappiness with penis size was less clear.