Frederickson, 24, skirted around questions about the negative reaction shortly after the finale, but told People in a new interview that she might have pushed herself too hard.
"Maybe I was a little too enthusiastic in my training to get to the finale," she told the mag.
Frederickson, who started out at 260 pounds also said she worked six hours a day in the three months leading up to the finale.
When asked if she developed an eating disorder, Frederickson said, "I am very, very healthy."
Dolvett Quince, the trainer who worked closely with Frederickson during taping, released a statement shortly after the show aired, asking viewers "not to look at one slice of Rachel's journey and come to broad conclusions."
But he has now admitted to People that Frederickson's weight loss "shocked" him.
"The first thing that went through my mind was, 'That's just too much,'" he said.
Here's how Michaels and Harper looked when they first saw her:
Harper recently told Rachel Ray that trainers don't see contestants when they leave the ranch.
"What people don't understand is, when the contestants leave to go home ... they're in charge of themselves," he said. "So, I had not seen her until that night, and so when she walked out, I was just kind of like, 'Whoa!' And I’ve been on the show since the beginning, forever," he explained. "I was stunned. That would be the word. I mean, we've never had a contestant come in at 105 pounds."
Michaels and Harper previously issued a joint statement distancing themselves from Frederickson's training regime.
"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," they said.