Season 12 kicks off with two new trainers - internationally renowned tennis star and certified trainer Anna Kournikova and top fitness expert Dolvett Quince - joining "Biggest Loser" favorite Bob Harper, and 15 contestants competing in a "Battle of the Ages" that will group contestants by age for the first time ever in the history of the show. Host Alison Sweeney tells the teams that they will make their first game-changing decision - who their trainer will be - in the order in which they finish the first challenge. Once each team chooses their trainer, "The Battle of the Ages" begins. The new contestants include Vinny Hickerson, who overcame a difficult childhood to become a successful Nashville recording artist, Antone Davis, a 447-pound father of four and former NFL player for the Philadelphia Eagles and Atlanta Falcons, and Bonnie Griffin, a 63-year-old grandmother of six who lost her home to Hurricane Katrina and lost her husband not long after.