The Biggest Loser (season 4) is the fourth season of the NBC reality television series entitled The Biggest Loser. The fourth season premiered on September 11, 2007 with 18 overweight contestants in a weight loss competition for an ultimate prize of $250,000. The Biggest Loser campus was located at California State University Channel Islands in Camarillo, California.
The season four contestants were divided into 3 teams: the Red team, led by trainer Kim Lyons; the Blue team, led by trainer Bob Harper; and the Black team, led by trainer Jillian Michaels. The teams were formed on the first episode, with the Red and Blue teams being selected by the two players who had won a foot race across the desert. The Black team was formed with the 6 remaining contestants who were not selected for the Red and Blue teams. While the Red and Blue teams returned to the Biggest Loser campus, the Black team was left behind, believing that they had been eliminated already. Instead, they remained in the desert and trained in secret with their trainer, Jillian, until they arrived on campus for the weigh-in at the end of week 2.

Fonte: wikipedia