A 100-year-old bodybuilder's No. 1 secret to living a long, healthy life: 'Know what you want to accomplish. Commit yourself to it'

For the past eight decades, Andrew Bostinto has trained for bodybuilding, and he still competes today at 100 years old.

This May, just four months after his 100th birthday, Bostinto won top honors and a championship belt at National Gym Association Inc.'s (NGA) physique contest. He's also the founder and CEO of NGA, a not-for-profit bodybuilding association.

"I never thought about getting old. This is what I do today, I'll do this tomorrow," Bostinto tells CNBC Make It.

Bostinto has had a lifelong committment to fitness. "I started much younger than 13. I was working out in the park already," he says. "I became good at it. I became a gymnast and hand balancer. Then at 17, I was already modeling."

He won "Senior Mr. America" at age 52 in 1977. But Bostinto, who is a World War II veteran, says that of all his achievements, he is most proud of his 29 years of service in the U.S. Army.