Spain's top fashion show has turned away a slew of models on grounds they are too skinny - an unprecedented swipe at body images blamed for encouraging eating disorders among young people.

Organizers of the pageant, known as the Pasarela Cibeles, used a mathematical formula to calculate the models' body mass index - a measure of their weight in relation to their height - and 30 percent of the women flunked, said the Association of Fashion Designers of Spain.

The association said Friday it wanted models at the show running from Sept. 18-22 to project "an image of beauty and health" and shun a gaunt, emaciated look.

The decision was made as part of a voluntary agreement with the Madrid regional government, said Jesus del Pozo, a designer who is part of the association, said Thursday.

Last year's show, also called Madrid Fashion Week, drew protests from medical associations and women's advocacy groups because some of the models were positively bone-thin.

This time the Madrid regional government decided to intervene and pressure organizers to hire fuller-figured women as role models for young girls obsessed with being thin and prone to starving themselves into sickness, said Concha Guerra, deputy finance minister of the regional administration.

Fashion shows, Guerra said, "are mirrors for many young women."

Del Pozo said this was the first time skinny models have been snubbed at a major international fashion show.

Ryan Brown, director of marketing and public relations in North America for the Elite modeling agency in New York City, agreed. "It is very unprecedented," said Brown, who has nothing to do with the Spanish show.

He welcomed the decision saying "I think it is great to promote health."

Madrid's show, which features mainly Spanish designers, is not as prestigious as catwalks in Paris or Milan but "it is not at the bottom of the pile," he said.

The impact of rejecting skinny women would have been greater at those other glitzier venues. Still, he said, "I am sure the industry is taking note."

The body mass index is a tool for doctors who study obesity. It is calculated by dividing weight in pounds by height in inches squared, and multiplying that total by 703.

If the resulting number is between 18.5 and 24.9, the person's weight is normal. Below 18.5 they are underweight. In the case of the Madrid show, organizers rejected women with indices under 18.

Brown of the Elite agency said fashion shows reflect the tastes of clothing designers, who for now prefer the Kate Moss look as opposed to the curvier dimensions of models such as Cindy Crawford in years past.

"They don't want voluptuous girls any more," he said. "It would be nice if fashion got back to that."

-Associated Press