Tosca Reno is defying the odds. At 53, the author and fitness expert refuses to subscribe to the stereotypes that accompany her age.

Instead, she is changing them. And, in the process, she's encouraging others to change their lives.

Reno, the author of 13 clean eating books, says the secret to being healthy and happy is eating clean. Her popular "Eat-Clean Diet" encourages individuals to drink plenty of water and eat six small meals daily, including a combination of lean protein and complex carbohydrates.

Put simply, clean eating is avoiding all processed food, relying on fresh fruits, vegetables and whole grains rather than prepackaged or fast food.

"It may sound counterintuitive, but eating clean allows you to eat more and weigh less because you are making smart food choices," Reno said. "I sometimes get criticized for using the word 'diet,' but the Eat-Clean Diet really is a lifestyle change that leads to healthy, steady weight loss and healthy eating for life."

Reno's advice to those wanting to change their lives is to first realize there is another way to live.

"This could come in the form of that 'a-ha' moment, when you suddenly catch a glimpse of your lumpy reflection in a store window, or perhaps after you receive some bad news at the doctor's office," she said.

"You just need that opening, that moment, when you finally decide to give yourself permission to change."

Reno's own "a-ha moment" came at 40. Unhealthy and in an unhappy marriage, she realized she must make changes. After divorcing her first husband, she began to see life differently.

"That was when I began seeing the world as having possibilities instead of limitations," she said.

At the time, Reno was overweight and was battling heart problems and hypoglycemia. She began going to the gym and decided to go back to school, where she met fitness guru Robert Kennedy, whom she later married.

"I didn't know who he was, but he said, 'Listen, I can get you into shape.' I soon learned who Robert was -- an icon," she said.

Kennedy, recipient of the 2012 Arnold Sports Festival Lifetime Achievement Award, became highly regarded in the fitness industry after founding Robert Kennedy Publishing, which has published 53 books and produces six fitness magazines.

Kennedy taught Reno how to eat healthily and work out, and Reno began seeing results.

"My physique changed. Everyone started asking questions ... I felt l was owning a secret -- that it is 80% nutrition, 10% training and 10% genetics."

Reno revealed her healthy secrets in her first book, "The Eat-Clean Diet." Since then, she has developed a large following of readers.

However, all the success in the world could not have prepared Reno for this past spring, when she lost Kennedy, her biggest champion, to lung cancer.

She said eating clean has helped her manage her grief and maintain her strength.

"I have abundant energy. My emotional energy is strong," she said. "I feel like when you have the nutritional army at work inside of you, you are that much more able to ward off depression."

Reno said she is determined to make her late husband proud. In addition to taking the reins at Robert Kennedy Publishing, she will compete in a figure competition October 13 in his honor.