A total of fifteen contestants are competing in the season, divided into three teams: Red, Blue and White.
Alison Sweeney first introduced the three teenage ambassadors who will compete in the game as the face of childhood obesity: Bingo, Lindsay and Sunny.
Afterwards, the trainers Bob, Dolvett and returnee Jillian face the crowd and re-introduce themselves to the new outreach of the show.
For the last-chance workout, the contestants still showed extreme struggle in the gym, especially for White Team's Nikki.
At the first weigh-in of the season, contestants received the surprising news of the Red Line, meaning the losing team's last placer would automatically be eliminated by the end of the night.
The White Team's motivation wasn't enough for Jillian, continuing with her "tough love" training method.
Because of their lack of working harder for the week, Jillian takes her team inside to personally improve and rejuvenate their skills.
For Week 2's challenge, Bingo, Lindsay and Sunny returned with their teams alongside NFL player Antonio Gates.
The White Team won Sunny's school a $5,000 grant and a visit with a fellow NFL football player.
On the second weigh-in, the Blue Team hit a strong note until Jeff's shocking zero-pound weight loss for the week.
As a result, Nathan fell victim to the red line with his five-pound weight loss, and was automatically eliminated.
The team who accumulated the fewest points would suffer the disadvantage of being isolated in a temptation room full of junk food and video games.
The Red Team suffered their first weigh-in loss, and faced the brand new elimination voting booth adjacent to the gym.
First aired January 21, 2013 The trainers left the ranch to work with the teenagers, leaving the adults to work-out on their own.
With a three-pound weight loss, Pam was eliminated automatically, leaving only one member still standing on the white team.
The weekly challenge was to have the contestants swim across a pond where they had to place ten 5-pound coins per player on each team into a fountain.
The winning team would have a choice: receive phone calls from home, or sell it for a two-pound advantage at this week's weigh-in.
Danni won the challenge and she elects to take the two-pound advantage at the scale, in addition to receiving 10 one-year memberships to Planet Fitness.
After much suspense, the scale showed Danni losing nine pounds, keeping the White Team alive for at least one more week.
First aired February 18, 2013 Week 8 started with a twist after Allison offered all of the contestants immunity, if they could collectively lose 70 pounds.
If the group failed to meet the goal, the person with the lowest percentage of weight loss would fall below the red line.
After a pop challenge about nutrition and a fitness test (where the kids served as ambassadors), the weight needed was reduced to 61 pounds.
Jeff, certain that he would be going home, was left speechless when Francelina only lost 2 pounds, falling below the red line.
First aired February 25, 2013 Week 9 began with a pop challenge that gave the winner a one-pound weight advantage.
By one brick, Joe won the challenge, placing 20 blocks to Danni's 19, and earned the one-pound weight advantage.
At the other challenge the contestants had to hold 40% of their weight or else they would fall seven stories, the last one standing would win immunity for that week.
Gina had to lay in a coffin until she told Jillian why she needed to be at the ranch, while Danni had to sing in public, Alex had to get down and dirty in the mud, and Joe had to swim 100 meters.
At the weigh in Gina lost 7 lbs with immunity she was safe, Jackson and Alex both fell below the yellow line by 1 lb.
First aired March 11, 2013 The contestants prepare for their final weigh-in on the ranch, where they'll do battle with not one but two elimination lines.
http://www.nbc.com/the-biggest-loser/video/sneak-peek-down-to-the-wire/n33492/ First aired March 18, 2013 All the contestants reunited for the finale (sans Nikki who quit the competition in week 1).