Promoting extreme thinness will become a criminal offence punishable by a jail sentence under a government-backed law that was tabled yesterday in France to combat anorexia nervosa.

The world’s first use of the law to tackle eating disorders is broadly aimed at the media and fashion world, but especially at the websites and blogs of the so-called pro-ana movement. While many are support groups, others promote starvation as a “life-style choice”, with girls and young women posting their wasting images as “thinspiration” for others.

Social networking sites such as Facebook and MySpace have come under pressure in Britain and other countries recently to ban their pro-ana entries.

Last month a website that originated in France caused an outcry for encouraging children as young as 9 to embrace plastic surgery and extreme dieting in the search for the perfect figure. The Miss Bimbo site invites users to create a virtual doll, keep it “waif thin” with diet pills and buy it breast implants and facelifts. The website attracted 1.2 million players in France.

Fines of up to €30,000 (£24,000) and a two-year prison sentence will be imposed on offenders who “provoke a person to seek excessive thinness by encouraging prolonged restriction of nourishment” to the point of risking death or damage to health. The prison term is raised to three years with a €45,000 fine if the person dies.

Some experts and fashion leaders oppose the Bill, which is expected to be passed by Parliament within months. “You do not solve this kind of problem with the law but with understanding,” Jean-Paul Gaultier, the designer, said. Didier Grumbach, head of the French Couture Federation, said it was not up to the state to legislate on beauty and aesthetic criteria.

The law, modelled on legislation for abetting suicide, was tabled by Valérie Boyer, an MP from President Sarkozy’s Union for a Popular Movement. Roselyne Bachelot, the Health Minister, gave it the Government’s blessing at the unveiling of a code for the media, advertising and fashion industry on “promoting healthy body images” and fighting anorexia.

“The pro-ana movements which spread their messages of death on the web must be the target for special attention,” Mrs Bachelot said as she presented Mrs Boyer’s draft Bill along with the voluntary code. Up to 40,000 people suffer from anorexia in France, the great majority of them girls and young women.

The 48-year-old elder daughter of Jacques Chirac, the last President, has been incapacitated for two decades with the disease.

Mrs Bachelot said that the “waif-like, diaphanous, transparent bodies on the walls of our towns, in our magazines and on our computer screens are exerting their power of harmful fascination on our society”. Anorexia was one of the most lethal of mental disorders, killing 20 per cent of long-term sufferers, she said.

Mrs Boyer, who has two teenage daughters, said that the new offence was necessary because “it was not possible to deal with the pro-ana sites under the law against provoking suicide or promoting cults”. She added: “We do not know who is hiding behind these sites, but there is real mental manipulation.” Her law was also aimed at magazines, she said.

It would probably be left to judges to define “excessive thinness” but this might be defined as a body mass index, she said. BMI rules have been set by some model agencies since 2006 when the Madrid fashion show imposed a minimum index of 18 for cat-walk models. This translates as a minimum weight of 56 kilos (8.8 stone) for a height of 1.75 metres (5ft 9in).

France banned last year a controversial Nolita advertisement featuring Isabelle Caro, a French model-actress who has written a book on her continuing battle with the disease.

The French voluntary code, which was drawn up by a panel headed by two eminent psychiatrists, commits the fashion, media and advertising world to raising acceptance of varied body shapes. “We undertake the promotion of diversity in the representation of the body, avoiding all stereotypes which could favour potentially dangerous canons of beauty,” the signatories said.

Marcel Rufo, a celebrity child psychiatrist who headed the code panel, said that he fully backed the use of the criminal law in fighting anorexia. The disease remains a mystery but everything had to be done to prevent vulnerable girls being encouraged to starve, he said. Among other new rules, magazines should be forced to mention that 60 per cent of their pictures are electronically retouched, he said.

I also think that in America or in any party of the world we should also have a law against pro-obesity too.

Thanks ONTD