In their rock anthem "My Generation," The Who sang, "I hope I die before I get old."

Nearly a half-century later, that could be the theme song for aging Who fans determined to live a long time without conforming to previous generations' notions of what "getting old" means.

This is not a generation that looks forward to retiring to a rocking chair on the porch.

Baby boomers intent on defying decrepitude are spending money to remain active and youthful—buying gym memberships, replacing creaky body parts, or swallowing batches of vitamins and supplements.

And that conjures potential profits for businesses that aim to lead boomers to the fountain of youth.

"All the research in the industry says clearly that baby boomers are much more interested in health. They want to live long lives and see their grandkids grow up," says Jim Sweeney, president of SuperSupplements, a retailer of vitamins and supplements in Seattle. "The folks who grew up in the '60s are committed to their health. They want to take control over what they do."

The number of adults age 65 or older is expected to reach 70 million by 2030, according to the American Geriatrics Society. The sheer size of the generation and its desire to fight aging are creating a business opportunity for the health-care industry. Joint replacements and nutrition are particularly popular with boomers.

"I think baby boomers are in a panic right now about their increasing ages," says James Altucher, author of "The Forever Portfolio," about the investment opportunities presented by the boomers.

"The recession is dampening, and even putting a backlash on the expensive procedures such as face-lifts, but what I call 'alternative biotech' is flourishing," says Altucher.

He says there's "an obsession" for less expensive supplements that are marketed as natural enhancers, such as resveratrol, a grape extract advertised as "America's anti-aging pill."

"I think this trend will continue," Altucher says, "although other, more 'medical' procedures such as Botox injections and removal of varicose veins will quickly become cheaper and mainstream."

Meanwhile, the number of hip and knee replacements is "skyrocketing" at Swedish Orthopedic Institute, in Seattle, says Administrative Director Heidi Aylsworth. The institute, which opened last year, has 10 operating rooms and 57 affiliated surgeons who do joint replacements.

Where patients once were told to delay joint replacement surgery as long as possible, new techniques are allowing patients to get their joints replaced before their lifestyle is severely affected by their ailments, Aylsworth says.

The institute's informational classes about joint replacement have been heavily attended. The boomers coming to the classes "are just sponges for knowledge. They come in with stacks of Internet information," she says.

"They're asking the right questions," Aylsworth says. "The volume of surgeries that the surgeons do, the infection rate. They're definitely more involved in the research and their care."

The institute is on track in 2009 to exceed the 2,500 joint replacement surgeries performed last year, Aylsworth says.

People are living longer with multiple chronic illnesses thanks to medical advances, but boomers hope to avoid or mitigate some of these ailments by living a healthy lifestyle.

"Older adults are using a fair amount of over-the-counter supplements and vitamins. We do see this in the turning-65 population. There is a large market out there," says Dr. Sally Brooks, a member of the American Geriatrics Society national board.

Boomers are getting their tips on what to take from their pharmacists "as well as, unfortunately, a little bit of what they see on TV or read in women's magazines or supplemental advertising," Brooks says. "Sometimes that can be problematic because these may not mix well with prescription medications."

But boomers have accepted the precept of alternative medicine guru Mehmet Oz, a frequent guest on Oprah Winfrey's TV show, that they can take years off their chronological age by eating right, exercising, and taking supplements.

"I'm a boomer. I'm 60, and I'm living proof of all that stuff," says Sweeney, of SuperSupplements.

Sweeney takes red rice yeast supplements to help maintain a healthy liver, along with Vitamin D to offset the lack of sunshine in the Pacific Northwest.

While pharmaceutical companies typically don't hold supplements in high regard, Sweeney says, more doctors than before are writing their patients prescriptions for supplements.