London is invaded by size-zero models (only this time they're men)

To the uninformed they look like the kind of nerdy boys that couldn't get the girl at the school disco, but after years of losing out to their beefy peers, the skinny male is having his day. As London Fashion Week kicks off this weekend, stick-thin men will be parading the catwalks promoting an ideal of male beauty that is a far cry from the bulked-up models of the Eighties and Nineties.

But as indie kids and fashionistas across the country squeeze themselves into the latest drainpipe jeans, fashion's move towards a male size zero has a more serious consequence: it heralds an era where men – like women – feel pressure to conform to a waif-like body image.

The masculine ideal has undergone a step change, putting pressure on young men to conform to a new body shape. The fashion expert and agent Johnathan Phang explained: "Suddenly, you've got lots of guys becoming models who never thought they could be; the sort of people who were normally considered weeds or nerdy-looking."

Phang believes there could be serious consequences for men who want to fit into the latest designs. "There is a pressure to conform to the size that's in fashion," he said. "If the trend is to be skinny, then men who follow fashion will want to be skinny so they can fit into the clothes. I'm 42 and fat as a house, so I've got nothing to prove, but if I was 20 now I would definitely want to be skinny and conform to my peers." This year the catwalks of Paris, Milan and, most noticeably, New York, were full of skeletal men in tightly fitting clothes. Like women before them, many male models are now expected to have an almost pre-pubescent frame.

It began in 2000 when the Christian Dior designer Hedi Slimane designed clothes for male models so young and slim that they barely looked old enough to be in secondary school. Since then the trend has hit the mainstream, with young men aspiring to the slimline look.

Devon Parsons, a male model agent at Select, said: "For the catwalk, the boy look is still ruling. In the Eighties and Nineties, it was very masculine and muscular; great tanned bodies and a really manly look. Now there's a trend to the more younger-looking, skinnier men."

Dylan Jones, the editor of GQ magazine, said that the recent trend for slimline men had proved problematic for the lifestyle publication. "Skinny models with skinny waists and skinny legs have been fashionable for the past few years, which makes it a problem when you're trying to photograph clothes that men might actually want to buy," he said.

"The sort of male models who have been fashionable recently don't look like they can afford to wear the clothes they're wearing, which at GQ's end of the market is something of a problem."

Eating-disorder charities have raised more serious concerns. A spokesman from the charity Beat said: "There does seem to be a growing trend towards men's clothes being designed for the slimmer male physique, and we're certainly aware of more men with eating disorders."

But the British Fashion Council admitted yesterday that a proposed scheme of health certificates for models – one of many suggestions after last year's inquiry into models' health – would not succeed until it was backed internationally