With millions of baby boomers reaching retirement age, fears are mounting of the economic impact if they follow the pattern of previous generations by curbing spending and draining Social Security and Medicare benefits.

But the 78 million boomers — born from 1946 to 1964 — have always broken the mold in terms of setting trends, and some investors and business and community leaders see their retirement as no different. They see an unprecedented, multi-billion-dollar opportunity to offer new products and services to an active demographic group that’s expected to live longer than previous generations.

When Elizabeth Reighard started her fitness training business in Myrtle Beach, S.C., four years ago, most of her students were in their mid-30s. But now her client list is made up mainly of boomers, such as Mary Smith, 58, who hired Reighard to help her “keep up with the grandkids.”

The demand for fitness trainers such as Reighard is expected to jump 24 percent over the next decade, largely because of baby boomers who want to stay healthy longer, according to the Department of Labor’s Occupational Outlook Handbook released in March.

“I’m seeing it more and more. Seniors know they have to be in better shape to have less aches and pains,” said Reighard, who’s also a boomer. “Yeah, we’re getting older, but our bodies feel good. . . . I look in the mirror and I might look 51, but I feel 25.”

The Census Bureau projects that Americans 65 and older will make up 19 percent of the population by 2030.

Community and business leaders in places such as the coastal towns of Myrtle Beach, Hilton Head and Bluffton, S.C., are looking to the growing retirement community to help rekindle local economies. They’re rethinking sporting and shopping developments, as well as art centers, to attract on-the-go retirees looking for an array of easily accessible activities.

On the labor front, the health care industry is the most obvious benefactor of a longer-living active community. Demand for home health aides is expected to grow 70 percent over the next decade, according to the Department of Labor.

Demand also will be high in less obvious fields, such as for architects, who will be called on to build senior-friendly communities; financial advisers, to help boomers plan their retirements; recreation workers, who’ll lead boomer-tailored excursions; and job trainers, who’ll teach the new workers called on to replace retirees.

“It’s only in Washington that 100 million people are viewed as an unaffordable cost and financial burden,” said Jody Holtzman, a senior vice president at AARP. “In the private sector, 100 million people are called a market and an opportunity.”

Concern about a drain on entitlements from retiring baby boomers has increased as talks intensify over avoiding the fiscal cliff. Boomers have been depicted as the elephant in the room. The Congressional Budget Office warned in June of a shortfall for entitlement programs, as aging boomers would consume a “significant and sustained” share of benefits from Social Security, Medicare and long-term-care services financed by Medicaid, the health care program for the poor.

Those projections fail to take into account that boomers are expected to work longer and they’ve never followed in the footsteps of previous generations, said Matt Thornhill, an author of Boomer Consumer, a book that examines marketing to the baby boomer generation.