In a life-altering competition, contestants use medically approved weight-loss techniques to shed pounds and try to win a $250,000 prize. The twelve players are seperated into teams - red and blue - and in the first challenge, pulling a heavy car across a track - the Blue Team prospers, but despite their advantage, the Blue Team also loses the least amount of weight at the weigh-in, and Dana becomes the first to be voted out.

After a tough elimination, the Blue Team gets back into the game on the second challenge, a bake-off which will determine the winner of a luxorious spa visit. The catch is that if any player takes a taste of anything they bake, 50 percent of all profits their team made is not counted. At the end of the task, the Red Team pulled through, making $362, edging out the Blue Team's $245. More importantly, the player's will power held strong, and no one took a lick of any food. At an emotional weigh-in, where neither Maurice, Lizzeth, Dave or Matt lose any weight, the Red Team is sent to the elimination ceremony, where Lizzeth is sent packing.

The Red Team and the Blue Team are forced to go onstage and perform about their feelings on their weight and weight-loss. The winner, decided by the audience at the nightclub which the players performed at, is the Red Team, who is given a reward. Later, even with the Blue Team training as hard as ever, the Red Team loses more weight than the Blue Team, forcing Blue to the elimination ceremony, where rumours and whispers divide their team. The deciding vote comes down to one of the Blue Team members, and Aaron is eliminated.

""Red and Blue Teams Go to New Heights"" - Blue Team trainer Bob Harper seems surprised after Aaron's ouster the night before. Things move on at the ranch, and after a workout, the players find a giant mountain of cupcakes in the house, with a note saying that whichever player eats the most cupcakes in 15 minutes would get to eat dinner with a loved one. After deciding on a method where no one would eat too many calories, Dave eats only one cupcake and is able to eat dinner with his wife, Tina. At the challenge, teams are forced to run up 1,500 steps to the top of a huge building. The Blue Team completes it more quickly than the Red Team, and are given a great reward. After a spat between Lisa and Jillian about effort, the weigh-in reveals that the Blue Team had lost more weight than the Red Team, and in the end, the Red Team chooses to send home Matt because of his failure to work with the team.

""A Team Lightens Up Through Elimination"" - After Matt's elimination Ryan realizes that Dave has been lying to him and the girls of the Red Team for the entire game. The challenge of the week is a food stacking competition - where team members must build their stack the highest using only their mouths and they may not eat any of the food during the game. The Red Team emerges victorious, giving them an amazing reward. However, the Blue Team comes out as the biggest winners; Andrea's 7-pound loss pushes their team to victory at the weigh-in, eventually leading to the Red Team eliminating the team member that is most annoying: Dave.

""Teams Trek to the Beach for a Challenge"" Rumours and suspicions fly after a tense previous elimination, where the women in the house assumed that the men were trying to pick them off. Players are just starting to get on each other's nerves: Maurice's lack of work ethic angers his team - and his trainer, Kelly Mac's backhanded compliments annoy the Red Team, and Lisa's whining continues to get on everyone's nerves. At the challenge, an agility competition meant to mimic lifegaurding, the Red Team prospers, winning themselves a trip to the Umberto Salon, where they receive makeovers and new hairstyles. The Blue Team, forced to vote one of their own off of the ranch, cannot decide who to eliminate. With a deadlocked vote, the members of the Red Team must choose to eliminate one of the members of the Blue Team, finally deciding on Kelly Mac.

""Biking Challenge"" Contestants race to log the most miles on a stationary bike before midnight, with a prize of better-fitting clothes as an incentive; participants learn of a new twist in the game.

The contestants are given an overwhelming surprise when they come face-to-face with their old, bigger, selves - cardboard cutouts as they apperaed the first day they arrived. The players run around a track with a weighted vest carrying the weight that each has lost so far. Ryan comes closest to his time from a previous run, winning himself immunity. At the weigh-in, Maurice and Lisa find themselves eligible for elimination, and when the other players vote, Ryan betrays his pinky promise with Lisa by being the swing vote for her ticket out of the house.

""A Lighter Side"" An often-comic look at the first eight episodes; previously unseen footage of contestants' exit interviews; bloopers; the contestants who cheated when they thought the cameras were out of range.

""Final Weigh-In at the Ranch"" It's payback time as the contestants turn the tables and ""train"" the trainers. This episode is the final weigh in at the ranch, preceded by the contestants reflecting on this journey that has changed their lives, and followed by a vote to trim the players' numbers down to three.

After weeks of training and careful eating tactics, the ""Biggest Loser"" is finally chosen, as the season finale comes about. The winner is decided during a live portion of the episode.

In this post-finale special, viewers discover more about the contestants' lives and competitive drive, including that of the Biggest Loser. Another weigh-in will take place, and one of the nine remaining contestants (less than third place) will win $100,000.