The 14th season of NBC's "The Biggest Loser" premiered Sunday night with big changes in the air for the extreme weight-loss show, including a brand new focus on childhood obesity and the return of Jillian!

For the first time, the weight-loss competition show featured three teenage contestants, 16-year-old Sunny, and Noah and Lindsay, both 13.

Though they will not compete to stay on the show or be weighed on camera, the teens are expected to participate in some of the ranch activities -- including rowing, cheerleading and obstacle courses -- to help reach a healthy weight.

Read more: 'Biggest Loser' trainer's weight tips!

In an emotional moment during the premiere, one of the teens, Sunny, opened up about her struggle with weight loss. "I always feel like people are looking at me and judging me for my weight, not for the person I am."

The teens (or "ambassadors for change" as they're called on the show) will also not stay exclusively at the ranch alongside the adults, but trainers will be checking in with them regularly at home to keep track of their progress and provide encouragement and support.

The other big change to the show was the highly anticipated return of trainer Jillian Michaels after two seasons away. Despite her time off to become a mother of two, Michaels showed she's not holding back, with three of her five teammates collapsing in the gym and another quitting the competition completely.

Amidst the tears, the show's emotional weigh-in also saw a big blow to her four-person team. TC, one of her group members, was eliminated for losing the least percentage of his body weight, but the check-in after the show featured the father of three running around after his kids, losing nearly 50 pounds from when he first started the show.