But rather than be a cause for celebration, Frederickson, 24, and her transformation has sparked concern that the 5'4" contestant may have taken her weight loss too far.
Frederickson started the show at 260 lbs. and, as a finalist, left the ranch weighing 150 lbs. to work on losing weight at home on her own. By the finale about three months later she had shed another 45 lbs. and weighed in at 105 lbs. to a size 0/2.
"I just love myself and I am embracing it," Frederickson told PEOPLE on Tuesday night, seemingly unaware of the concern over her appearance.
In a statement, NBC and show production company Shine America said, "We support Rachel and all of The Biggest Loser contestants who have shared their journeys over the past 15 seasons. We remain committed to helping contestants achieve healthy weight loss and live healthier lifestyles, and to inspiring viewers to do the same."
The show's trainers – Jillian Michaels, Bob Harper and Dolvett Quince – are remaining mum about their reactions to the finale.
"Jillian Michaels will not comment on Rachel's journey as she was not her trainer. She is celebrating the at-home win of her contestant, Tumi. Any questions about any of the other contestants on the Biggest Loser should be directed to the show’s producers," a rep for Michaels tells PEOPLE.
Harper posted a similar message on Facebook: "Jillian and I want to take a moment to congratulate all of the BL contestants on their hard work. We're not comfortable commenting on Rachel's journey because we weren't her trainers and weren't given an opportunity to work with her at any point. Any questions about the contestants on The Biggest Loser should be directed to the show's producers.
But one source who works closely with the show says people were shocked by Rachel's transformation before the live finale. "Executives honestly thought that maybe she'd look okay and that no one would notice," says the source, "but people gasped."
When asked by PEOPLE how many calories she had been ingesting daily leading up to finale, Frederickson avoided answering with specifics. "I am in maintenance mode now so it is just balancing it with life and making sure that I work out and eat right and healthy and make good choices," she said.
Frederickson says of the Biggest Loser experience: "I came here to gain back my life and I did exactly that."