(CNN) -- 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.
In the competition, Reno will be judged on leanness, muscularity, muscle symmetry, evidence of athleticism, poise, grace and confidence. She said her late husband is providing her with all the confidence she needs.
"His teachings are guiding me through this," she said.
Each day, Reno goes to the gym, which she calls her "drug of choice," and does "reps for Bob."
"I'm rebuilding myself," she said.
Reno advises all who begin the Eat-Clean Diet have a clear purpose in mind to power them through the process.
"Anything new is challenging or different," she said. "But it becomes second nature very quickly."
She advises dieters to envision the end result, just like one would envision arriving at a travel destination.
"I think you have to have your mind set in place," she said. "What does the end result look like?"
Once a goal is determined, Reno said individuals must prepare their surroundings to support that goal.
"Clear your cupboards of all junk foods and then start planning healthy meals and shopping for clean food," she said. Reno's books contain meal plans, grocery lists, recipes and motivational tips to help.
Always having clean food available is key, Reno said.
"When you're cooking dinner, double the recipe and pack the extra food for the next day's meals -- I call these 'planned leftovers,' " she said. "This will make it super easy to just grab a healthy meal when you're pressed for time. Also, when you leave the house, make sure you take a cooler filled with your healthy meals for the day."
Reno suggests setting weekly and monthly goals and writing them down. "People who write down their goals are 50% more likely to succeed."
Whether easing into the Eat-Clean Diet or diving head first into it, Reno said it's important for dieters to be committed to the process.
"You're never going to get to your goals unless you're willing to do what you need to do to get there," she said.
The most important way to achieve those goals is to manage time properly, Reno said.
"Plan your meals and training sessions for the week and try to delegate chores whenever possible. Once you get into a routine, you'll realize that the whole process is not as hard as you imagined."