Jillian Michaels is returning to "The Biggest Loser," and she's going to put all her weight behind tackling childhood obesity.

Fitness expert Michaels, who has been on and off the show since its first episode and most recently departed the reality series in late 2010, will be back for the upcoming 14th season, which will premiere in early January, NBC said Tuesday.

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Michaels will join returning trainers Bob Harper and Dolvett Quince. The upcoming season will also feature celebrity guest stars.

In addition to Michaels' return, "The Biggest Loser"'s next season will feature child contestants for the first time, in an effort to highlight the national epidemic of childhood obesity. Competitors from ages 13 to 17 will appear on the upcoming season, along with adult participants.

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"As a former overweight teen, I know firsthand how dramatically weight issues can affect every aspect of a child’s life,” Michaels said in a release announcing her return. ”Having recently become a mother of two, I am more passionate than ever about helping empower children and families with the information and resources they need to live a healthier life.”

Contestants will be divided into three teams supervised by Michaels, Harper and Quince,  with each team including at least one underage competitor. While the child contestants won't be eligible for elimination, they will contribute to their teams, and their progress will be featured in each episode.