American health officials are warning of a dangerous new trend: girls as young as nine using illegal steroids to pump themselves up to resemble their favourite stars.

More commonly abused by athletes, the body-building drugs have become increasingly popular with schoolchildren, many looking to artificially acquire more curves and body tone.

'Kids are taking steroids for looks,' said Dr Linn Goldberg, head of the Division of Health promotion at the Oregon Health and Science University. 'They want to look sexy, they want to get bigger and they want their bodies to be better toned. Unfortunately, they are ignoring the damage they are doing.'

Studies claim that up to 7 per cent of middle school girls (ages nine to 14) and 5 per cent of high school girls (14 and older) have tried steroids, in the form of a testosterone cream, pill or injection, at least once. The drugs are readily available over the internet or from pushers in gyms or at school.

Changing values among America's youth explain much of the attraction. The waif-like bodies of the skinny supermodels of the 1990s have given way to more popular role models such as Jennifer Lopez and Beyoncé, who have fuller, toned figures.

Such evolving fashions can be hugely influential on young minds, Goldberg says. 'Look at how models have changed over the last 40 years. Nowadays girls see magazines with pictures of women with six-pack abs.'

Most states randomly test schoolchildren for 'recreational' drugs such as marijuana and cocaine but have shied away from testing for steroids for financial reasons. It costs about $120 for full urine and blood analysis.