An all-new twist shakes up the fifth season premiere of "The Biggest Loser," heightening the emotion and tension in the competition. For the first time ever in the history of the show, teams of two will compete against each other rather than individuals. Ten teams - including a mother and son, husband-and-wife, best friends, brothers and a divorced couple - have to pick their trainer, weigh in and compete in challenges together. This week, the teams will have to pull a giant hot air balloon across a field, with the winner getting a coveted 2 lb. advantage at the first weigh in.

The nine remaining teams are surprised by the news that Bob and Jillian will be training them together as one team. Then the contestants are tempted by a delicious barbecue buffet, and the challenges get more difficult as they are tasked with riding giant seesaws! In the end, one more team is sent packing.

The remaining eight teams compete in a game of "elimination" where the last team standing wins immunity so they can't be sent home this week. While the challenge causes rifts in the house as the players become more competitive, the trainers are determined to work the teams harder and post more impressive numbers on the scale at this week's weigh-in. Then an elimination round follows, and another team is sent packing.