Bridges attended high school in Nelson Bay, New South Wales. In an interview with The Sydney Morning Herald, she said "I was 14 when I pitched the idea to my school mistress that I would take the kids at school who didn't play sport, who hung around smoking cigarettes, and do fitness classes with them." She then went on to take over space at a local squash court along with her personal trainer Tash Sheehy and taught classes there. At 18, Bridges graduated from the Australian Institute of Fitness as a certified fitness instructor, and has served since 2009 as an ambassador for the organisation.
In 2007, Bridges became a trainer on The Biggest Loser. In her first season, she trained the red team alongside Jillian Michaels. She appeared as the red team trainer for every season. In 2016, Bridges announced she was leaving the series.
Bridges has appeared on the Nine Network's Mornings with Kerri-Anne as a women's health and fitness expert.
Bridges was one of the contestants in Celebrity MasterChef Australia. She describes herself as "a bit of a foodie" and won the second heat with her signature dish of Moroccan spiced lamb with eggplant and currant couscous, beating performer Kathleen de Leon Jones and journalist Peter FitzSimons to continue in the competition.
Bridges regularly appears as a guest on shows such as Can of Worms, The Project and Sunrise.
In addition to her TV appearances, Bridges is the author of several books, including:Crunch Time: Lose Weight Fast and Keep it Off
Losing the Last 5 Kilos: Your Kick-Arse Guide to Looking and Feeling Fantastic
Crunch Time Cookbook: 100 Knockout Recipes for Rapid Weight Loss
The No Excuses Cookbook
Losing The Last 5 Kilos
5 Minutes A Day
Everyday Weight Loss
Your Best Body
In 2012, Bridges launched the fitness and leisure range ONEActive, sold in Big W stores across Australia. This includes hardware fitness goods, footwear and apparel. Her fitness wear ranges in sizes from 8-26. In August 2013 her apparel was launched on the BIG W website and in September 2013 she established a licence agreement to also sell kitchenware with the retail chain. Also in September 2013, Bridges expanded her apparel to include children's fitness clothes for ages 8 to 16.
In 2010, Ubisoft brought Bridges to Canada to help develop the weight loss segments of their product Your Shape Fitness Evolved. The company used motion capture to create an avatar of Bridges to appear in the game, which will use the Kinect technology. Bridges said "It was quite extraordinary. I'm now a fitness trainer inside an XBox game." Bridges said fitness games could provide as good a workout as going to the gym, saying "If you can roll out of bed and turn on your Xbox and get into it games like this one, you've just cut your travel time to get the gym, to find a park and you're good to go. There's a real opportunity to spark a passion to get into your fitness."
Michelle Bridges started the online 12 Week Body Transformation 12wbt.com in 2010. The program, to date, has lost over 2,000,000 kilos from the Australian public and worldwide participants.
Bridges married fitness trainer and gym owner Bill Moore, who later became her business manager, in 2003. The couple separated in May 2013 and Bridges began dating fellow Biggest Loser trainer Steve Willis. She currently resides in Sydney. In July 2015, the couple announced they are expecting their first child together. Bridges gave birth to a son on 19 December 2015.