At 80, Jazzercise's Founder Is Thriving. She Credits Lean Protein, Weightlifting, and Treating Herself to a Daily Dr Pepper. Jazzercise brought in $77 million worth of sales last year and has more than 2000 locations worldwide.

^{This article originally appeared on Business Insider.}

More than 50 years after the launch of Jazzercise helped pioneer the group-fitness industry, its founder, Judi Sheppard Missett, still loves to dance every day.

Now 80, she continues to teach classes and do choreography for her company, which has more than 2000 locations worldwide, more than 55,000 customers in the U.S. alone, and brought in $77 million worth of sales last year.

Missett continues to play a role as executive chair instructor in the company, which is now a family affair; her daughter, 55, has taken over as CEO and chief choreographer, and her granddaughter, 22, is an instructor.

She told Business Insider she believes her longevity probably has something to do with the fact she's very active but relaxed about her fitness and nutrition. She eats her protein and veggies and drinks a daily Dr Pepper, her favorite treat.

While she follows a weightlifting routine and takes long walks at the end of each day, her priority is making time for other people.

"I have more things to do in life, and I want to be able to enjoy them. I want to be able to enjoy my granddaughters and just everything that's going on in life and in the company as well for as long as I possibly can," Missett said.

She built a community around fun, accessible fitness

As a lifelong dancer, Missett said her goal as a 25-year-old instructor in 1969 was to bring her love of movement to others, especially women who felt as if exercising was a chore. She noticed her classes, which initially focused on traditional techniques, weren't getting a lot of return students.

"They all said: 'We love the class. It's great, but it's really difficult. We don't want to be professional dancers. We just want to look like they do,'" Missett said. "I thought maybe I just need to make this simpler and more fun."

She changed her approach to teaching, turning students away from the mirror, instructing them to follow her lead instead, and doing simplified choreography with lots of encouragement and motivating, high-energy music.

The first session in this new "Jazz Dance for Fun and Fitness" class had 15 students.

By the third class, her clientele had quadrupled to 60, which soon grew to more than the studio in Evanston, Illinois, could handle.

"The room wouldn't hold anymore because people were telling their friends," she said.

From there, Jazzercise began a community that spread — first to California, where the company is now headquartered, and then globally.

Missett thinks of it as a family. What she loves about her job, and what keeps her getting out of bed in the morning excited to start the day, is that sense of purpose.

"I really loved this so much because it was exposing people to dance and the joy of movement and the joy of music. There was a spirit behind it, and there was a camaraderie in those classes," Missett said. "I feel like we had an impact on helping women understand what they can accomplish and how powerful they could be. It meant everything to me. And it still does."

Lifting weights keeps her strong and prevents injury

Still a devoted Jazzercise fan, Missett stays active with strength training and walking, too.

"I have a motto, and the motto is, keep moving so you can keep going," she said.

Her daily morning routine includes 20 minutes of lifting weights, and she isn't afraid to go heavy. She said the routine keeps her back healthy, and being strong helped her recover more quickly from a recent hip replacement.

"When people get to be older, you'll have a little bit of pain here and there and a few little creaks and whatnot in your body. For some people, it's an excuse to stop doing things, but it really shouldn't be because if you keep moving, it really helps most of those things," Missett said.

She avoids fad diets in favor of moderation

Missett said her approach to nutrition is to focus on getting plenty of protein and leafy greens with her meals. Lean protein sources such as beans, chicken, and fish can help with satiety and maintain muscle, and green veggies are rich in nutrients such as antioxidants for healthy aging.

But having a little treat is just as important for her routine.

"If I want to have a hot fudge sundae, I'm going to have it," she said. "I just want to do what I do in moderation and eat as best I can."

That includes her daily habit of drinking a Dr Pepper, which she's loved since childhood.

Dietitians typically don't recommend sweet beverages such as soda. They suggest limiting added sugars to 20 to 25 grams per day (the average soda has about 40 grams of sugar). Artificial sweeteners in diet drinks can also have downsides.

For Missett, the enjoyment is worth the trade-off.

"It just brings me joy," she said.

After decades of watching wellness trends come and go, Missett isn't a fan of fads in dieting or anything else.

"I think people get into fads and think: 'Oh, I've got to do this. I've got to be on trend.' No, you don't," she said. "Do what works for you. And if the trendy thing isn't working, find something else."