A 79-year-old triathlete didn't get fit until her 40s. She shared her 5 longevity tips for healthy aging.

This 79-year-old Ironman triathlete only started running in her 40s. Here are her tips for being as fit as she is at almost 80.

• Cherie Gruenfeld didn't start her fitness journey until her 40s.
•  Now she's 79 years old and training for her 29th Ironman Triathlon.
• She shared her tips for people who want to be as fit as she is at her age.

In her 40s, Cherie Gruenfeld was active but not fit. But that changed when she watched the Boston Marathon on TV one morning in 1986.

Gruenfeld was working a demanding sales and marketing job in Boston, and didn't think much about fitness apart from going on the occasional hike and bike ride. But by the time the marathon was over, Gruenfeld had decided she would run the 26.2 miles the next year.

She began training right away, and 6 months later that October, she completed her first marathon in three hours and 26 minutes. She'd fallen in love with running and started doing multiple marathons a year.

Then, in 1991, she picked up a magazine about that year's Ironman Triathlon in Kailua-Kona, Hawaii, which consists of a 2.4-mile swim, a 112-mile bike ride, and a 26.2-mile run.

Gruenfeld's husband, who'd supported her fitness journey since the beginning, encouraged her enter — even though she was by no means a swimmer and didn't even own a bike.

So, she joined a local pool, bought a bike, and took a six-month leave of absence from her demanding job to train.

In October 1992, at 48 years of age, Gruenfeld crossed the finish line at Kona.

"I had planned on it being a one-and-done thing, but my first words to my husband were 'I love this, and I know how I can do it better next time,'" she said.

So she did it again. And again and again, completing a total of 28 Ironmans in 31 years.

She even trained while being treated for two cancers, one under her arm and one in her breast.

"I spent a bit of time in total disbelief just thinking it couldn't happen to me. But that gets you nowhere, so I just built a new plan: to stay healthy during my surgery and treatments and to postpone my Ironman return until I could. And I did exactly that," she said. "I trained every single day except for surgery day during that whole period of time. I was very lucky. I never suffered — I just rode my bike."

And her Ironman career isn't over — Gruenfeld is training for her next triathlon, which she will compete in as an 80-year-old.

"I love the sport, and I hope to be a part of it until I can't. I don't know when that will be, but it's not today," she said.

Although our genes likely play a large part in our longevity, experts not only agree it's never too late to make positive changes, but that they can be relatively simple to have an effect. That will heartening to anyone put off by the buzz around time-consuming and expensive regimens like that of multimillionaire tech exec Bryan Johnson.

Create good eating habits

Gruenfeld said that she improved her diet to the point where, when she looks for something to eat, she consistently goes to the healthy foods, she said.

Experts say that consistently making healthy food choices is far better than trying and failing to achieve "perfection" all the time. The 80:20 rule — choosing healthy foods 80% of the time and being flexible the other 20% — is one way to make this easier, dietitian Nicole Ludlam-Raine previously told BI.

Get good sleep

We all know we should try to get enough sleep, but few of us actually prioritize it. But it's one of the most important things you can do for physical and mental health, Dr. Meena Khan, a neurologist and sleep expert at Ohio State University, previously told BI.

"You've got to try to get a good night's sleep every night because that's when your body regenerates," Gruenfeld said.

Surround yourself with support

"Get friends who are doing things you admire, and get out there with them. They'll encourage you, and it'll be much better for you," she said.

"My husband believes I can do anything. If I told him I was going to win the Ironman — take the overall win, and not just age-group win — he'd say 'Go for it!'"

Research shows that people with positive relationships are more likely to live longer, as they are though to reduce physical and emotional stress, and can even boost your immune system.

Never give in to age

"When we're younger, we tend to take on anything. But as we age, we sometimes lose that confidence and free spirit. But we have nothing to lose and everything to gain by continuing to just go for it," Gruenfeld said. "We will all age, but we don't have to get old."

Dr. Heidi Tissenbaum, a molecular, cell, and cancer biology professor at the University of Massachusetts Medical School, previously told BI that keeping the mind and body active is the most important factor in longevity.

Take care of your body

Gruenfeld said she tries to look after her body especially if she's training or exercising hard.

"Rest, ice, stretch, strengthen," she said.

Mobility training, which involves stretches and movements including squats and pull-ups, can give you the range of motion and strength to stay independent into older age, Ben Foster, founder and head coach of the People's Athletic Club, told BI.