The star, known for her work as a T.V presenter as well as being part of the famous Osbourne family, revealed the staggering scale of her weight loss on social media.
Kelly Osbourne weight loss
Osbourne shared a snap on Instagram, prompting Mamamai - mother of influencer Jeannie Mai - to comment: "Oh my gosh, you lost a lot of weight."
Replying to the comment, Osbourne wrote: "That’s right mamma Mai I lost 85lbs since I last saw you. Can you believe it? Kaakakaka."
According to the Daily Mirror, the star has credited her plant-based diet with helping her lose weight and improve her relationship with food.
Osbourne once said she put pounds on after overcoming her drug addiction, saying: "I replaced the drugs with food and just got fatter and fatter. I'm an emotional eater. When I get upset, my diet goes out the window."
'A life change'
While she lost 30lb (2 stone and 2lb) after appearing on Dancing with the Stars in 2009, it wasn't until she went plant-based in 2012 that she lost the majority of her weight.
Speaking about her new lifestyle, she told HuffPost: "Once I learned how to work out right and eat right, it’s one of those things that you just have to commit to a life change rather than being on a diet."