Season 10 kicks off with a new theme of "paying it forward" and 21 contestants vying for a spot at the ranch to get healthy and change their lives forever. With obesity now one of the leading causes of preventable death in the United States, "The Biggest Loser" wanted to broaden their reach this season, pay it forward and motivate communities - not just contestants - to get healthy. So trainers Bob Harper and Jillian Michaels and host Alison Sweeney travel to seven cities in the premiere episode, with each trainer leading community fitness challenges like a one-mile race or a 500 step-up competition. In each of the seven cities - Detroit, Los Angeles, Portland, Atlanta, Phoenix, Oklahoma City and Boston - there will also be three contestant hopefuls competing in the challenges. The two candidates who complete their fitness challenge first win a spot at the ranch, while those who don't make it will get a chance to vie for a spot on the show in a later episode. Guest starring in the premiere will be three popular past season contestants -- season eight winner Danny Cahill, season seven finalist Mike Morelli and season five finalist Mark Kruger.