This photo taken Aug. 19, 2009 shows a large display of women's plus sized clothing at a J.C. Penney store in Miami. Plus size brands are aiming to create sexy and sleek designs like never before, but customers are not buying clothes at the rate they used to.

MIAMI –The American waistline may be expanding, but plus-size shoppers are tightening their belts.

People just aren't buying plus-size clothing at the rate they used to. Apparel in general — being a discretionary purchase — is suffering because of the economy, but plus-size has been particularly hard hit.

According to the NPD Group, a market research company, the overall women's apparel business is down about 5 percent and plus-size is down almost 10 percent from the 12 months ending in May 2009 compared to the same time the year before.

It's hard to account for the dip at a time when more than half of American women are estimated to wear plus-sizes, generally considered size 14 and up, but analysts have some theories.

"The stigma still continues despite the majority of the population is overweight," said Marshal Cohen, chief retail analyst at NPD. The stigma means some retailers don't want to lure overweight customers and send out the "wrong" image, experts said, and the customers themselves may feel put off by many stores.

Some retailers, including Old Navy, Banana Republic and Ann Taylor, have taken their plus-size collections out of stores and are selling only online — which some experts say plus-size shoppers prefer. Others, including H&M, have dropped out of the plus-size market.

Several years ago, stores had made an effort to expand the plus-size market, but they have basically abandoned that during the recession, Cohen said.

"They've made feeble attempts at going after it, but now that business is challenged, it is first thing knocked out of the store," he said. "Even though they built it, this was not a field of dreams for the retailer."

And there's also the uncomfortable connection between obesity and lower incomes, which might help explain the dip. A study of nationally representative data on American workers by two professors at Stanford University found that obese workers at the same level of job experience, education and gender earned less than their thinner colleagues.

For women, there was a statistically significant difference of wages of $2.64 per hour. For men it was 58 cents per hour, which wasn't statistically significant.

"The recession has hit workers hard, obese (workers) are hit particularly hard," said Jay Bhattacharya, associate professor of medicine at Stanford University.

Christie L. Nordhielm, associate professor of marketing at the University of Michigan, said that if overweight people are paid less, it would make sense that they would cut down on buying clothes.

"If they are stressed about paying their mortgage they are not going to be in a clothing store getting this year's hot new look," she said.

Still, several brands are reaching out to plus-size customers. Lane Bryant is launching a couture-inspired line called the icon Collection by Lane Bryant in September, while Forever 21 has launched a plus-size line called Faith 21.

And for some retailers, plus-size clothing remains a relative bright spot.

"I will say that the general apparel and upscale retailers is soft and large sizes is no worse — a little better — than the apparel," said Frank Doroff, Bloomingdale's vice chairman and general merchandise manager for ready-to-wear.

Bloomingdale's sells plus sizes at 80 percent of the stores across the U.S., and Doroff said the department store is trying to add brands that cater to plus sizes. The store carries lines including Lauren by Ralph Lauren and Jones New York.

"We need to give better service and better assortment," he said, adding that plus-size customers buy a lot of other items in the store. "It's the value of that customer, not simply what clothes they buy."

Recent reports accused the company of cutting floor space for plus-size clothing at its New York City flagship store and offering fewer lines. Liz McGovern, Bloomingdale's Director of National Media Relations, said the department was moved because customers indicated they wanted to shop on the same floors as other women, and that the amount of inventory is not specific to plus size. It is an industrywide trend.

Other department stores Macy's and JC Penney also say they are working to court the plus-size customer.

"She wants to look good, feel fashionable and look good in clothes. And she wants fashion," said Nicole Fischelis, group vice president of ready-to-wear fashion at Macy's. "We offer the same trends we address with our regular-size customer."

Marianne Stone, divisional vice president in women's apparel for JC Penney, said the store's plus-size business has increased over the last years, but wouldn't give specific numbers. She did say lines like Unity and nicole by Nicole Miller were added and that the store offers plus-size customers "the same fashion looks, same fashion trends that we have in missy."

"We are really doing whatever we can to offer this customer fashion," she said "She's hungry for it."

Stone agrees that stigma is a big problem for this market, with retailers not making a big enough effort to attract the plus-size customer, but she added that JC Penney spends a lot of time bringing in a variety of people and doing fit seminars, to make sure the clothes are cut properly for the different body types.

"We are one of the leading businesses at JC Penney," she said. "In this economic environment I don't think anybody is in a growth mode."