Researchers from Victoria's Deakin University interviewed 70 children aged eight to ten to identify what body shapes boys considered ideal, and compare those with the body ideals of prepubescent girls. They found that by the age of eight children already had definite body ideals, which are influenced by their peers, the media and gender stereotypes.

While girl ideals centred around being skinny and beautiful, boy ideals were intertwined with sporting culture and ability.

"Boys often chose the term fit as it described an ideal body which encompassed their dislike of fatness, the importance they placed on physical abilities, and their preference for masculinity," the study to be published in next month's issue of the Body Image journal found.

Deakin researcher Gemma Tatangelo said she didn't expect boys so young to have such firm and detailed body ideals. "Boys are really concerned with being good at sport and that has big implications for body image and the way they look - and how comfortable they are with the way they look."

Young boys said sportsmen were their favourite celebrities (because of their physical skills), sports games their favourite TV programs. They often cited television weight loss program The Biggest Loser and said they wanted to look like the trainers on the show.

Ms Tatangelo said her research suggests that by adolescence boys' body ideals would be even more firmly established, thus making them much more difficult to change.

Boys associated fitness with sporting ability and muscularity and thought they would be happier if they were more muscular because it meant they would be stronger and better at sports.

Playing sport (usually some form of football) with peers was the main lunchtime activity for boys, and influenced their body ideals. They reported pressure to be good at sport, and said those who weren't would be excluded by others.

Butterfly Foundation chief executive Christine Morgan said body image anxiety among young people is worsening. "Young people link their value as a person to a particular body size or shape," Ms Morgan said.

"They think 'unless I conform to what the ideal looks like [skinny for girls, muscular for boys], I'm not going to be successful'. It goes to the core of their self-worth."

Young, handsome and looking to be perfect

A camera comes out and the first words from one of this clutch of mates bonding at Bondi Beach on Saturday? "OK boys, now flex."

For these young men there is no denying body image pressures play a regular role in their lives. Protein shakes are a daily norm in their diet to keep them in the best - and biggest possible - aesthetic condition.

Johan Philip, 18, says that in his life body image is about achieving peak masculinity.

"It's all about who's the macho, who's the dominant male. And that isn't something new either, that been around forever," he says.

All are actively involved in athletics, but say that pumping iron and getting ''ripped'' require an entirely different sort of workout.

As members of Gen Y, they say social media is a big part of their lives and is most commonly the feeding ground for the ideals of body image and its subsequent pressures.

According to Mr Philip, Facebook and other social media amplify the pressure to look good.

''Especially Instagram,'' he says. ''It's an outlet for body building companies to use, models to use and then we follow them and we aspire to be like them."

They all agree that achieving recognition on social media through ''liking'' has a huge impact on whether they are socially accepted, and to what degree.

"I think 'likes' are really important. You want to have good photos on Instagram so you can rack up a lot of likes, and then come the girls,'' says Mr Philip. ''It's a case of 'can you please like or comment on my photo so it comes back up in the feed'."

But Joe Hardy, 18, says not everyone is on edge about "how many likes they pull in''.

"It's not that important, I mean everyone has different views on it, but I don't need it," he says.

At 21, Mitch Milnes says body image concerns still exist.

"You've gotta look ripped to get girls in the summer," he says. ''And you're always competing against your mates about who's bigger.''

Not only social media, but also real-life social events are demanding: "You've gotta get ripped for stereo,'' he says.

By Lucy Cormack