Michaels, who is returning to the show after leaving in 2011, admitted that she was surprised about the attitude of some of the participants.
"In previous seasons, contestants came into this house and respected the experience," she told TV Guide. "They gave themselves to the process.
"Some of the current crop work hard to fail and then gloat in their failure. They'll go, 'See? I told you that you were wrong'. We're three months into filming - the fact that we're still dealing with this now is outrageous to me."
While Michaels added that some of the contestants are "amazing", she admitted that she has already told some of them to go home.
Michaels, who has an adopted daughter and baby son with her partner Heidi Rhoades, also revealed that motherhood has not affected her training style.
"Everybody was like, 'You're going to be so much softer'," she said. "And I really wanted to be, but it's not the case. I feel like aspects of my business and home life are being sacrificed for me to be here, and I need that sacrifice to be worth it.
"It's as bad as it's ever been. It's worse than it's ever been, actually... I started out with five contestants, and by the end of the first workout, only one was left standing in the gym."
The new season of The Biggest Loser, which will feature child contestants for the first time, will premiere on Sunday (January 6) on NBC.