Rachel Frederickson made headlines earlier this year after winning the 15th season of “The Biggest Loser,” but it was for all the wrong reasons.

Frederickson lost 155 pounds, going from 260 lbs to a stunning 105 lbs. Many felt she looked stick-thin on the season finale, and wondered whether she had been pushed her too far or become anorexic. Even two of the show's trainers, Jillian Michaels and Bob Harper, said they were stunned by Frederickson's appearance and felt she had lost too much weight.

Four months later, the 25-year-old admits she was taken aback by the reaction to her weight loss.

"It was quite shocking, really," she told CTV's Canada AM Thursday.

Frederickson says she had been a swimming state champion in high school and simply became determined to win.

"I'm a former athlete and I went on the show to get my life back, and I absolutely did that. And the athlete came out," she said.

"For me, I thought, 'I'm up against two big guys and I have to try.' And that's exactly what I did. I worked really hard and I ate really healthy and showed up on the stage feeling great."

Since claiming the $250,000 prize, the voiceover actress has put back on some of the weight she lost. In April, she said she was back up to 125 lbs. These days, she's no longer interested in talking about the number on the scale or about losing weight to look a certain way.

"What I really learned is it's not about a number and I’m not going to define myself by a number… So that, for me, was the biggest gift: to know that no matter what I look like, I’m happy with me and I accept myself," she said.

Before the show, Frederickson says she hid in her life, staying at home most of the day. When she decided she wanted to change, she wanted to do it in a big, public way, and sent in a tape to apply for the show.

Her weight loss has transformed her life, Fredrickson says and even though some of the weight has come back, she says she's in her comfort zone.

"I'm so happy. Before, I let fear make all of my choices. And now, I've branched out and become part of my community and started a new job," she said.

"I'm still doing voiceover work, I'm making so many friends, and I think, 'Gosh, what a world of difference a year can make when you make the decision to make that change'."

Frederickson is now working to promote Biggest Loser Resort Niagara, a fitness and weight loss retreat in upstate New York. Her advice to others who want to make a change and lose weight is to commit to one small step that will set you on the right path.

"For me, the step was making that video. But it just takes one step," she said. "Commit to yourself, commit to your health."