SAN FRANCISCO (Business 2.0 Magazine) - There is no polite way to say this: Americans are fat, and they're getting fatter. More than 60 million Americans are obese, up from 23 million in 1980. Another 28 million are expected to join their ranks by 2013.

Forget the stereotypes: It's not just people in low-income neighborhoods who are packing on the pounds at McDonald's (Research). Researchers at the University of Iowa have found that obesity rates are rising most rapidly among urbanites who earn $60,000 or more per year.

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Heretofore, the main business response to this overwhelming demographic trend has been the $49 billion weight-loss industry. But now a much broader segment of corporate America has begun to see the nation's fattening for what it is: a potentially powerful driver of consumer demand across a wide swath of the economy.

Just as baby boomers have driven business and shaped the economy during the past half century, the "plus-size" population is likely to dictate marketing trends through much of the 21st.

Already, greater girth is forcing American business to rethink -- albeit carefully -- the way it designs and sells everything from sofas and toilets to clothes.

The new Toyota (Research) Rav4 comes with seats up to 3 inches wider than prior models. Select Comfort, the high-end mattress maker, now sells a grand king size that's 30 percent bigger than a traditional king.

Market research firm Mintel estimates that U.S. sales of women's plus-size apparel jumped 50 percent during the past five years to nearly $32 billion. Dana Buchman, Tommy Hilfiger (Research), and Ralph Lauren (Research) now make clothes to fit larger women, and even Jessica Simpson has slapped her name on a new brand of big-bottom jeans.

But it's not just Fortune 500 companies getting in on the action. Small entrepreneurs are tapping into the big business -- often for surprising reasons. Take Tim Barry: The 55-year-old management consultant had no intention of launching a company, much less building a million-dollar business. He was just frustrated.

Several years ago, as Barry boarded a plane in Boston bound for San Francisco, he heard flight attendants discussing how they would handle an especially sensitive problem with seating. At 6-foot-1 and 365 pounds, the stout Barry and several other heavyset passengers needed seatbelt extenders—standard equipment on most airplanes to accommodate larger customers.

But there weren't enough to go around, and Barry overheard the humiliating options being considered: They might ask the bigger passengers to squeeze into a standard belt, or, if they couldn't, boot them off the flight.

Crisis was averted after airline workers found some extra belt extenders inside the terminal. But Barry didn't want to ever be put in the same situation again. He decided he would buy his own seatbelt extenders and make them part of his travel kit, along with his noise-reduction headphones and Tom Clancy novels.

Barry hunted around the Web, in catalogs and travel magazines, and even at private airports. No luck. There was, it seemed to Barry, a nationwide shortage of airline seatbelt extenders on the retail market. It was then that Barry's frustration began to give way to the invigorating tingle that hits every business veteran at the first whiff of an entrepreneurial opportunity.

Barry first contacted the manufacturers that supply the airlines. Soon thereafter he began mapping out plans to launch a retail site, called Extend-Its.com, from a small warehouse near his home outside Vancouver, Wash., to provide seatbelt extenders directly to the abundant numbers of people who need them. To date, Barry has shipped more than 10,000 belt extenders at $60 to $70 a pop.

And he's launched two other sites, Scale-It.com and SuperSizeWorld.com, to sell household supplies and hard-to-find convenience items for heavyset customers: $20 Hangerzillas that hold coats weighing as much as 100 pounds, high-capacity scales and extra-large plush bath towels that go for $60 apiece.

This year, with just two employees, Barry expects to hit $1 million in sales. "I've done nothing but Google ads," he says. "The demand is there, and the market is wide open."

While Tim Barry and several other retailers sell household convenience items, Aitan Levy is making the same kind of bet with bathroom fixtures, another market that big business has been slow to adapt for the obese.

The owner of a small plumbing manufacturer based outside Los Angeles, Levy had heard people complain for years that standard toilet seats are too small, uncomfortable, and fragile for stout customers.

So three years ago he designed the Big John Toilet Seat, a 19-inch throne made of reinforced plastic, and started making the seats himself. In the first two months, he sold about 2,000 commodes at $88 apiece, and he has since rolled out a newer $170 model and added a $160 open-front version.

Demand has doubled over the last six months. "All you have to do is look around to see that people are bigger," Levy says. "But where are all the products and services?" Levy's toilet line is not yet profitable, but he expects it to be by year's end. Industry heavyweights Kohler and American Standard, meanwhile, have yet to unveil rival products.

The opportunities, in short, seem about as unlimited and surefire as these things get. "I just don't see how I can lose," Barry says. "If we know anything about medical history, once you get past a certain weight, you're probably not going to lose it. You'll be my customer for life."

This is an excerpt from a story in the June issue of Business 2.0. To read the complete version, click here.