'The Biggest Loser' trainer Jillian Michaels is about to face her most difficult challenge this season. The show's producers are bringing the biggest contestant ever to the show: Michael Ventrella, who weighs in at 526 pounds. His size and the size of other contestants this year has Michaels worried.

The tough-love trainer shows her concern for the contestants' medical safety. "The contestants keep getting bigger and bigger," Michaels tells Ladies' Home Journal. "As the trainers we have no say over the challenges. We worry about them too."