When NBC's hit reality fitness series, "The Biggest Loser," kicks off on Jan. 4 for Season 11, it will be the last time fans get to see trainer Jillian Michaels whip people into shape.

The 36-year-old recently announced on Twitter that this season will be her last, saying that she's ready to pass the torch to someone else and move on. "When I look at the platform I was able to have because of the show, I wonder what else I could be doing with it or should be doing with it," she told PEOPLE. "I want to be a part of getting PE back in our schools. I want to be a part of getting organic farms subsidized. I want to be a part of these solutions. It's where my heart is at and where my head isat."

Michaels, a self-described "sustainable pescatarian," has been a big supporter of organic, all-natural food in schools, especially in the fight against childhood obesity. In late September, she teamed up with the Physicians Committee for Responsible Medicine to ask her fans to support the Improving Nutrition for America’s Children Act — a bill that was eventually put aside by the House in favor of the Senate's Healthy, Hunger-Free Kids Act, which was recently signed into law.

“I’m the tough trainer on 'The Biggest Loser' and 'Losing It with Jillian,'  and I am passionate about helping people reach a healthy weight,” Michaels said then. “But I’m writing to you with a request that just might put me out of business. I want you to help fight childhood obesity so that fewer people will need to go through the difficult process of shedding excess pounds. More than a third of America’s children are now overweight or obese.”

But it's not just these causes that are pulling Michaels away from "The Biggest Loser" — a future family is also part of the decision. "I love 'Biggest Loser,' " Michaels says, "but it's a seven-day-a-week job. I'm 36. I want to start thinking about a family. I want to be a mom … I need to be able to find a way to incorporate that in my life."

"The Biggest Loser" premieres on NBC on Jan. 4 at 8 p.m. EST.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Jillian Michaels leaving 'The Biggest Loser'
Personal trainer for hit reality series to focus next on physical education in schools and subsidies for organic farms.