Teenage girls shrug off the health dangers of aspiring to the super-thin images of female beauty portrayed in western society, specialists warn, amid a heated debate on skinny models.

  As a catwalk ban in Spain on fashion models deemed too thin stokes controversy in the world's fashion capitals, a French endocrinologist warned that 15-20-year-olds are "a generation formatted in thinness."

  "The young population of today has only seen thin people on the front page of magazines, on posters at the bus stop, in the underground," Annie Lacuisse-Chabot told AFP.

  She welcomed the move by the Madrid organizers of the "Pasarela Cibeles" fashion week, which kicked off Monday, to bar five models whose body mass index (BMI), calculated on a height-weight ratio, was too low.

  But fashion professionals here have defended the trend for super-slim.

  "Weight has nothing to do" with the choice of a model, said one official from a large model agency, speaking on condition of anonymity. "One looks at a girl as a whole, one never looks at the weight."

  But he conceded: "They are asked to respect their body, to not gain too much weight."

  Karen Pfrunder, casting director at Reflex Event, which specializes in organizing catwalk shows, reiterated that a model's weight does not come into the equation. Rather, she said, the criterion is for 90-centimeter hips (36 inches).

  "When you are 1.80 meters (5.9 feet) it's harder to have 90-centimeter hips," she acknowledged, adding, however, that "fashion is like that; it always has been like that."

  The issue has already cast a shadow over London fashion week, which also began Monday, the second stop after New York and ahead of Milan and Paris of a whirlwind month-long fashion fest.

  French magazine Elle took the initiative two years ago to keep extremely thin models off its front cover, also applying the BMI defined by the World Health Organization.

  BMI measures body fat based on height and weight; it is thought that a model measuring 1.75 meters (five feet nine inches) in height would have to weigh at least 55 kilograms (121 pounds) to comply with the stipulation.

  The restrictions have triggered media speculation about whether models like Kate Moss, reportedly 1.68 meters (5 feet 6 inches) and 49 kilos (108 pounds), could be affected.

  While it is possible to be very thin and healthy, others are simply under-nourished, Lacuisse-Chabot said, pointing to nutritional deficiencies, notably in protein that can lead to fatigue, as well as problems with periods and fertility.

  But psychological problems, such as less resistance to stress, depression, the onset of eating disorders, even anorexia and suicide, can also be sparked, she warned.

  For about 20 years, women and girls with a perfectly normal body mass index have been consulting doctors about losing weight, but the trend is now a social phenomenon and affects ever-younger girls, a Paris symposium heard in 2003.

  A study published at the time showed how women tended to believe themselves to be fatter than they actually are.

  At the start of the 1980s, winter editions of women's magazines already showed very thin models on their covers but swathed in coats or hats, according to the study by the Paris-based Institute of Political Sciences.

  Since 1985, models have stripped right down, regardless of the season.

  "In Western societies, we have moved from a deep, very old latent anguish, over a lack of food and fear of famine, which valued a body enveloped in reassuring fat, to an ideal model of near skinniness, whilst we live in a time when we have more food to eat and more security than ever before," anthropologist Annie Hubert, research director of France's national centre of scientific research, said.

  But thin looks are set to remain a la mode.

  "Thinness remains synonymous with elegance, and that is not anywhere near changing," commented Sylvie Fabregon, of the 'Plus' department dedicated to plumper models at the Contrebande model agency.

  Agencies "pick very tall girls, very thin, so that clothing falls better," she said, adding: "If the agencies take rounder girls, the designers are going to look for models elsewhere, thinner people will no longer buy."

  Nevertheless a ban would change nothing, Fabregon conceded.

  She suggested instead "daring to say 'look how ugly it is'" in magazines referring to a photo of an overly-skinny model, rather than stating "before summer, lose three to five kilos."