Beth Ditto and Jean Paul Gaultier

Singer Beth Ditto models fashions by French designer Jean Paul Gaultier in the spring-summer 2011 show. (Pierre Verdy / AFP / Getty Images / October 1, 2010)

By the numbers it just doesn't seem right. Nearly 65% of American women are overweight, according to the National Center for Health Statistics, and of those, more than 35% are obese. Yet most designer collections end at size 10. And on hundreds of high-fashion runways at international fashion weeks this month and last, ultra-slim models were wearing trendsetting designs that will never be manufactured in sizes to fit most American women.

In a time when retailers are struggling to turn a profit, the disconnect between fashion and reality is a puzzle. The fashion world's emphasis on tall, thin and young women is frequently cited as contributing to poor self-esteem, anorexia and bias against the overweight.

What's more, a key finding of a 2009 report by Mintel, an international consumer market research firm, found that plus-size shoppers, especially younger women, want fashions that match those sold in smaller sizes.

But that's a big request with a small chance of success, experts say. The proportions, economics and aesthetics of plus-size fashion virtually guarantee that fashion — fashion of the trendsetting, desire-stoking, magazine-filling kind — will always favor the thin.

Creating stylish clothing for larger women isn't as simple as making bigger sizes of existing styles, says Rosemary Brantley, chairwoman of fashion design at the Otis College of Art and Design.

"There are a lot of styles that won't size up," said Brantley, a designer and former model. Pattern makers can more easily enlarge or shrink proportions for sizes 0 to 10 because the body's proportions expand in a more universal manner in the lower sizes.

"The human form is nothing but a bunch of curves," Brantley said. "Those curves get very exaggerated as one gets bigger. The more exaggerated the curve, the more seaming, the more shaping, more darting, more fitting and more expense."

Marshal Cohen, chief analyst for the NPD Group, a retail and consumer behavior research firm based in Port Washington, N.Y., puts it this way: "There is a very different science to the plus-size business. Half of what goes into the garment is different. Not all fabrics or techniques can translate to the plus-size customer."

Indeed, designers adept at making regular sizes often are not trained in techniques to maintain the correct fit and proportion of plus-size clothes.

The design process also requires larger mannequins and fit models on which to fine-tune samples, a significant investment of time and money for manufacturers or fashion schools.

Brantley and other fashion academics say design students have no interest in plus-size design, and as a result, few schools offer extensive courses in the specialty. To fit the multiple body proportions, retailers that cater to larger sizes often resort to carrying boxy, shapeless styles that accommodate a variety of body types.

In fashion classrooms and design studios, the human figure is proportioned to emphasize the clothing, not the body. Fashion illustrators traditionally use a body that is divided into nine or 10 sections, each the length of the head; the normal human body is seven to eight heads tall.

On the typical fashion figure, the distance from waist to knee is exaggerated and the legs are tremendously long, said Eddie Bledsoe, associate professor of fashion design and costume history at the Otis College of Art and Design.

"The stretched-out torso, defined waist and narrower hips ... make the clothes look and hang better," he said. Further, a lean body with subdued curves allows the flat planes of most clothing to drape without interruption.

"That's fashion. That's high fashion," Bledsoe said. "It's for the social elite, the aristocracy. It's not for the average person. That's the difference between high fashion and consumer or mass fashion."

Though runways and fashion editorials make clothes seem irresistibly glamorous, Bledsoe pointed out that "the fashion runway is art. It's a show; it's theater." And those magazine images? They're retouched, the clothes are pinned and altered, and the models aren't wearing them to be comfortable.

Yet with every edition of "Project Runway," and every behind-the-scenes blog entry or snapshot, high fashion's thin mystique blends ever more into popular culture, where its familiarity stokes expectations. The thin figure is ubiquitous. Models are no longer rare creatures who exist in faraway fashion ateliers; they're stars of talk shows, reality television, actresses, wives of rock stars and even fashion designers themselves.

"Our eyes have been trained to accept the proportions of the nine-head figure," said Kaye Spilker, curator of costume and textiles at the Los Angeles County Museum of Art. "The more we see of it, the more it becomes normal and seems attainable," she said.

Throughout fashion and art history, a plump human form was more often the aberration than the norm, as well.