The research also found eight-to-18-year-olds who'd been bullied were more likely to consider using muscle-enhancing drugs (15%), not eat (15%) or undergo cosmetic surgery (18%) to attain the ideal physique.
It also found half of them feel social media puts pressure on them to look good, while a quarter believed a "perfect body" actually exists.
More than half also believe that eating disorders such as bulimia - where a person binge-eats before forcing themselves to vomit - affect boys just as much as girls.
56% of boys said they'd find it hard to talk to teachers about how they looked, with 29% struggling to discuss it with parents.
Speaking on Premier's News Hour, Bill Stevenson, from the Boys Brigade, said: "We deal with thousands of young men and particularly teenagers and they're very conscious now that there's much more advertising about the male image.
"They'll try to get to the gym more and they're more conscious about it than I was when I was a boy.
"Perhaps if the advertisers and those involved in marketing didn't always have that perfectly honed body when they're advertising, if they tried to project a wide variety of people I think that would help much better.
Listen to Premier's Hannah Tooley speaking to Bill Stevenson on the News Hour:
