A source tells People the 40-year-old trainer is currently upset by several aspects of the show. Michaels has been with the series for 12 of its 15 seasons; she was temporarily replaced by Kim Lyons in season 3, and officially left for seasons 12 and 13.
"She's deeply concerned about the direction the show has been taking," the source tells the magazine. "She is turned off by the mean-spirited story lines and poor care of the contestants."
The "poor care" referred to includes the treatment of season 15 winner Rachel Frederickson. Michaels was not the champion's official trainer, and she and fellow trainer Bob Harper were visibly stunned when the contestant appeared on the show's finale looking extraordinarily thin. Frederickson had gone from 260 to 105 lbs. on her 5'4" frame, and has since gained back 20 pounds.
"Michaels wants to distance herself from the Biggest Loser brand," the source elaborates. "Especially considering what happened with Rachel, her feeling is that there isn't proper attention paid to the contestants' health or wellness."
"They've asked her to come back to boost the ratings and they need her, but the Rachel thing shook her up," the person continues. In addition, "The show uses her as the bad guy, and anyone who knows Jillian knows she's not the bad guy at all. She's a loving mother of two kids. She's not the negative person they portray her as. She wants to be in a place where she has more respect."
Casting has already begun for season 16 of The Biggest Loser. A premiere date has not been set for the new season.