Back in 2014, Rachel won the 15th season of the show, losing 59.6% of her body weight. She went from 260 pounds to 105 pounds, dropping 155 pounds. At the time, critics said she took the show too far and lost too much weight. She ended up gaining 20 pounds quickly after the finale to reach her "perfect weight."

Jillian was one of the show's personal trainers for the first 15 seasons, but left the show after that 15th season.

At the time of her departure, NBC said, "After helping hundreds of contestants transform their lives and inspiring millions of viewers at home, The Biggest Loser and Jillian Michaels have decided to part ways and she will not be returning for season 16 when it airs in the fall."

The reason behind her exit was revealed in the Netflix docu-series Fit for TV: The Reality of The Biggest Loser.

"This was actually when I quit the show, permanently... We had a contestant, who was not my contestant, and I still profited off The Biggest Loser. I take responsibility for being a part of a show that allowed this to happen. Personally, I wouldn't have allowed it to happen, but I profited off a platform that did. And this is when I was like, 'Okay. I'm complicit and I have to leave.' But a contestant named Rachel Frederickson walked out onto the stage during the finale. I hadn't seen her, Bob hadn't seen her. And she was unhealthily thin, to say the least. And nothing good came out of that, I am 100% positive, with regard to her health. Go ahead and hate on it. Hate on me for being part of it. Have at it," Jillian told host Thomas DeLauer on the podcast.