Gripping an 8-pound dumbbell in each hand, Richard Fassler sank into a deep squat, hips well below knees, and popped back up. It looked painful, but Fassler, a youthful, wiry, 73-year-old retired economist, breezed through his reps, then danced in place, demonstrating some boxing moves he’d taught himself.

His smile was so genuine and his banter so upbeat, as he fist-bumped with friends at his gym, that it was difficult to believe Fassler is battling prostate cancer.

“I’m a warrior, not a survivor,” he said. “I am someone going through cancer right now.”

Regular vigorous exercise, Fassler believes, is a potent weapon against the disease. “I work out for an hour every day,” said Fassler, who worked for the state’s Department of Business, Economic Development and Tourism and has lived in Hawaii with his wife, Karen, for 43 years.

“It requires a tremendous amount of discipline, but the cancer is a strong motivator,” he said.

Fassler was diagnosed with prostate cancer in January 2013 and had surgery to remove his prostate. Four months later the prostate-specific antigen in his blood tests began to climb, signaling a recurrence, and he was put on hormone therapy to lower it.

Hormone therapy, though, could have nasty side effects, including hot flashes and muscle weakening, Fassler said. A lifelong tennis player who met his wife on a tennis blind date, he preferred to combat the cancer with intensive exercise and a change in his diet.

“There are some risk factors you can’t do anything about, namely, age and genetics,” Fassler said. Although prostate cancer can strike men of any age, the risk rises after age 50 or if one’s father or brother has had the disease.

“Then there’s lifestyle, which you can do something about.” To try to keep his prostate cancer from growing, Fassler follows the Mayo Clinic’s recommendations: Eat a diet low in red meat and dairy fats and high in fruits, vegetables and fish; and avoid being overweight.

“It’s basically a heart-healthy diet and weight-control regimen,” said Fassler, who stands 5 feet 9 inches tall and weighs 150 pounds. Lean all his life, he exercised to gain back the weight he lost after surgery — “I’ve got much more muscle,” he said — and now focuses on staying at this healthy weight and not gaining body fat.

“If you’re sedentary and have excess fat tissue, cancers thrive and can even become more aggressive,” said Fassler’s doctor, Charles Rosser, a urologist and oncologist at the University of Hawaii Cancer Center.

“Exercise reduces fat and releases endorphins, the body’s own natural upper,” Rosser said.

As a result of his lifestyle changes, Fassler has been able to go off hormone therapy.

On a recent weekday morning, he demonstrated his daily workout at his regular gym, the 24 Hour Fitness on Kalakaua Avenue in Waikiki. He no longer plays tennis or jogs since he developed plantar fasciitis, a painful foot injury that makes low-impact exercise a priority.

He starts by riding 30 minutes on a stationary bicycle on the club’s second-floor lanai overlooking the waves at Kuhio Beach. It’s a view that makes exercise a pleasure, Fassler said.

Urged by his daughter, Kim, to try spin classes on stationary bikes — “At first I looked and thought no way I can do that, I’m the oldest person here” — he took one with her and was hooked. He’s added two 45-minute classes a week to his schedule and finds he can keep up with the group. “The instructor directs you to sit down or stand up, gear up or down,” he said. “The classes are brutal — you’re outside and you sweat a lot.”

Strength workouts — a rowing machine, a lat pull-down station and free weights — come next.

“This is for the biceps, which senior citizens need for lifting luggage, garbage, laundry,” he said at the lat pull-down machine. “You’ve got to strain. That’s the way you build muscle.”

In addition to keeping his own cancer in check, Fassler said his goal is to raise awareness of prostate cancer, which is the most commonly occurring and second most fatal cancer among American men.

Every year in Hawaii, approximately 800 cases of invasive prostate cancer are diagnosed, and more than 100 men die from it, according to “Hawai‘i Cancer Facts & Figures 2010,” which contains the most recent data on the disease.

Yet outside of his prostate cancer support group at Kuakini Medical Center and consultations with his doctor, Fassler complains that no one seems to be talking about it. Why is that? Prostate surgery can result in erectile dysfunction, and men are reluctant to discuss sexual problems, Fassler said, adding that he hopes that sharing his positive results will inspire all men, as well as other prostate cancer patients, to adopt a healthier lifestyle.

“I feel fantastic knowing that I’m doing everything in my power to live a longer and healthier life,” Fassler said, noting that the No. 1 killer of U.S. males is heart disease, with cancer a close runner-up.

Which means, he concludes, that with his heart-healthy workout and diet, he might live longer than if he’d never had cancer.

"Good Fit" spotlights inspiring fitness stories of change, self-discovery and challenge, and other fitness-related topics. Tell us what motivates you and how you stay fit and healthy. E-mail feature@staradvertiser.com.