What reality show features celebrity fitness trainers Jillian Michaels and Bob Harper?

The reality show featuring celebrity fitness trainers Jillian Michaels and Bob Harper is The Biggest Loser.

The American version premiered on NBC in 2004, following contestants competing to lose the largest percentage of their body weight. Michaels and Harper were prominent trainers during the show's early seasons, often leading rival teams and coaching contestants through workouts, diet changes, and weigh-ins.

The program became known for its dramatic transformations, elimination ceremonies, and a cash prize for the contestant who achieved the greatest percentage of weight loss. Jillian Michaels appeared in multiple stretches of the series, while Bob Harper eventually became its host in addition to his trainer role.

A common mix-up is confusing The Biggest Loser with fitness programs or documentaries featuring one of the trainers individually. The title refers to the contestant who loses the largest percentage of body weight, not to the trainers themselves. The format was later adapted in several countries, including Australia.