Frederickson, 24, dropped from 260 pounds down to 105, losing almost 60 percent of her body weight. Her thin frame sparked concern online with many viewers pointing to the look of shock on the faces of trainers Bob Harper and Jillian Michaels when Frederickson stepped out.
"I feel amazing. I feel truly alive and just transformed," she told E! News at The Biggest Loser finale. "I couldn't be more happy, more thankful to get this second chance to take charge of my life again."
Frederickson said planning is the key to maintaining her weight loss.
"I make sure that I plan ahead," she said. "I cook my meals; make sure I'm ready for the week and that I have some snacks prepared. If my day is really busy with work, I have a snack prepared and ready to go so that I don't have to take the quick fix. I eat five times a day. The key, really, it's in the kitchen, you got to work hard in the kitchen, too."
Her workouts will now be "fun," she said. "I'm going to choose something different," she said, "[Like] spinning and yoga and pilates and weight-lifting. If you can incorporate fun into it, it just makes it so much better."
American Idol winner Ruben Studdard joined Frederickson during this season of NBC's The Biggest Loser.
"This changed my life immensely. It was a life or death situation for me that had to be handled. This was the wakeup call I needed to kickstart my new life," Studdard told E! News.
His regimen now includes an hour and thirty minute workout every morning.
(E! and NBC are both part of the NBCUniversal family.)