EXCLUSIVE: Lee Majors' Fountain of Youth Secrets Revealed — How Staying Active, Dieting and His Positive Mindset Keeps Him Going Strong at 86

Lee Majors looks like six million bucks – he's fit and trim at age 86 as he was five decades ago when he was The Six Million Dollar Man, RadarOnline.com can reveal

And Majors isn't done yet – for his birthday in April, he shared on his Instagram account: "Another year around the sun ... and while the calendar might say 86, I like to think of it more as '68' with a few bonus chapters. Here's to living well, staying sharp, and aging like the legends do."

Married to his fourth wife, Faith Noelle Cross, since 2002, Majors is living his best life in his golden years.

"He's had enormous success, as everyone knows, in shows like Six Million Dollar Man and The Fall Guy, both of which are still rerun hits," an insider pointed out. "But he's staying humble and living every day to the fullest. He dotes on Faith, and she thinks he's a dreamboat."

At the height of his fame, Majors had a high-profile marriage to Charlie's Angels beauty Farrah Fawcett, his second wife. They were truly Hollywood's golden power couple. Their relationship lasted a dozen years, their 1973 marriage ending in 1982.

Today, Majors works hard to maintain his svelte stature.

"He exercises daily and eats right and stays on top of the grooming, too, so much that no one would know he's 86," said the source.

"He stays active making appearances at events to meet and greet fans, and Hollywood is calling him to do cameos and smaller roles in TV shows and movies."

And he may have found his personal Fountain of Youth in the love of a good woman. His 1961-1964 marriage to Kathy Robinson produced a son, Lee Majors II, now 63.

After his relationship with Fawcett failed in 1982, Majors tied the knot with 1985 Playboy Playmate of the Year Karen Velez in 1988. They had a daughter, Nikki Majors, 37, and twin sons, Trey Kulley and Dane Luke, 32, before divorcing in 1994. Then he found Cross.