She was the Red Team trainer until 2006, when she was replaced by Kim Lyons.
Jillian returned to the show in 2007 as the Black Team trainer.
She and Bob Harper are also the trainers on the Australian version of the show.
Jillian was overweight as a child, and her mother enrolled her in martial arts classes.
She took hold of that, got herself in shape and became determined to help others get in shape as well.
(She's been practicing Muay Thai and Akarui-Do for 17 years now)
Jillian's workout for her clients blends kickboxing, yoga, Pilates, plyometrics, and weight training together, giving them a total package.
Besides The Biggest Loser, Jillian hosts a Sunday talk radio show on Los Angeles' KFI (640 AM).
Jillian released a video game for the Nintendo Wii called Jillian Michaels Fitness Ultimatum 2009 in October 2008.
You can find out more about Jillian at her website here