"I went from a size 22 to a size 4. I never even knew 4 existed," she said in an appearance on "Good Morning America" today.
Vincent, 5 feet, 5 inches tall, had weighed 234 pounds. A former competitive swimmer, she maintained her healthy swimmer's appetite even after she left the sport, and as a result, slowly gained weight -- 5 pounds each year for 13 years.
Vincent admits she used food as a crutch, explaining that she'd tried many different diets before going back to her old habits.
"The small changes [are] what helped me," she said, adding that she started out by getting on a treadmill for one minute, getting off, then getting back on again for another minute.
The mantra that spurred her on was "believe it, be it," and she's now taking that positive message to her new challenge: Her new show, "Live Big With Ali Vincent," through which she aims to help others who are struggling with their own weight problems.
She'll take a hands-on approach, helping them not only in the gym but at home, too, where she will teach them how to eat better to achieve their goals, get them involved in new activities and help them learn how to overcome psychological obstacles.
Vincent has also written a book about her experiences, "Believe It, Be It: How Being the Biggest Loser Won Me Back My Life."
As for her secret to keeping the weight off? She has a simple, no-excuses mandate: Exercise anywhere, anytime.
"I do lunges in grocery stores, I do squats in lines. I jump rope in an airport," she said.
Someone can burn 20 calories with little effort. "Who cares what other people think?" she said of her unusual exercise venues.
She acknowledges that exercise is a hard work.
"After 10 minutes, I want to quit," she said, but added that she keeps going by focusing only on the next 10 minutes.