This piece originally aired August 12, 2015.

A remarkable 77-year-old woman is reshaping more than her body, by breaking a sweat. Constance Tillet is living proof it's never too late to push yourself in the gym, reports "CBS This Morning" co-host Norah O'Donnell.

Keeping up with her today, it's hard to believe that just a few months ago, Tillet's body was failing her.

She's been through more than just two hip replacements.

"Two knee replacements, two rotating cuffs -- a partial and a full," she said.

But all that couldn't stop her from turning her life around.

She believes it's important for seniors to be working out.

"Get up and do it. Stop with the whining," Tillet said. "Stop with 'Oh you have to take care of me.' Take care of yourself."

Constance Tillet at CrossFit South Brooklyn CBS News

That's something Tillet didn't used to do. Her health problems started almost 30 years ago, when she was 50. She took insulin four times a day for diabetes and 60 pills to treat high blood pressure, congenital heart failure and arthritis.

Then last fall, Tillet's son suggested she try CrossFit, and helped her find CrossFit South Brooklyn.

She said she never worked out until now.

Tillet met gym owner David Osorio and, after just 10 months of working out together, she is down to just a few pills a day, and has lost 50 pounds.

"People have this perception that, you know, you have to be some really exceptional physical genetic person to kind of come in and make tremendous progress like this, but it's just about consistency," Osorio said.

And there's strong evidence that movement improves seniors' health. In the largest study on the issue, by the National Institute on Aging, doctors followed more than 1,600 seniors over a two-year period. They found that regular and moderate physical activity reduced the risk of disability by 18 percent.

Osorio said he has been most impressed by Tillet's attitude.

"People love seeing her. She lights up the room when she comes in," he said.

Constance Tillet at CrossFit South Brooklyn CBS News

Osorio said there's a psychosocial element to fitness.

"Part of all this is meeting people and expanding your social base and just having more people in your life that you can depend upon and that you can trust," he said.

For Tillet, that moment came in June when her devoted husband, the man who took her to every CrossFit session, died suddenly, on the same day he was scheduled to start his own fitness plan.

"He was my nurse, my doctor, my friend, my everything," Tillet said. "He was my encouragement. He's still my encouragement."

That encouragement, Tillet said, will keep her working out. She said it's changed her mentally and spiritually.

"When my husband died and the word spread, in my wildest dreams I never thought they would be there with me, and they were there with me to his grave site," Tillet said. "And they are still with me and they will be with me till I leave here. South Brooklyn CrossFit is my family, my children, and I mean it with the bottom of my heart."