Howard Stern's longtime radio co-host, 58, who says she could barely walk a couple of city blocks a few years ago, completed a remarkable three-year return to good health this weekend by running the New York City Marathon.
"My life totally changed, and now I have this amazing amount of energy," Quivers told PEOPLE at New York City's Dbar after the race. Having lost more than 80 pounds and switching to a vegan diet, she says, "Changing my body has given me the ability to do all these amazing things that I never in a million years imagined I could do."
A 26.2-mile run, of course, was one of them.
"It was something that was never on my radar," she says. "Then I thought, why not just do it? Why not just throw my body out there and try and see what I can do?"
Quivers admits the second half of the race was a struggle, but adds, "The positive thing is that I now know what I need to do to get my body in better shape and keep it up for the next one."
Overall, she's light years from where she was, in terms of her overall health. "I wasn't well," she says. "I just wanted to feel better. I had no idea that once I found out what was making me feel better, it would actually rejuvenate me and rejuvenate my life."