The Biggest Loser is an NBC reality television show that began broadcasting on October 19, 2004. It involves twelve contestants who are overweight to varying degrees participating in a contest to lose the most weight. The show is hosted by comedian Caroline Rhea and is narrated by current Endurance host, J.D. Roth, who serves as creator and executive producer of the show. Bob Harper and Kim Lyons are personal trainers assigned to help the competitors. Jillian Michaels was a personal trainer for the first two seasons and the special editions. This show got its start in the United States on the US network NBC, and the show has since gone international.