Osbourne, 26, the season 9 runner-up, transformed her body after the show was over, and is now a size 2. Returning to the program this week for its 200th episode, she credited viewers, and her old dance partner Louis van Amstel, for the change.
"Louis van Amstel and Dancing With the Stars changed my life, and as cheesy and cliché as that sounds, America had a hugest part in that," she tells Access Hollywood.
"By picking up the phone and voting for me every week, and all the amazing things they said, [they] gave me the confidence to keep going at something that I was so scared and so terrified to do."
Osbourne says she cried when she saw her bikini photos in Shape. "It was a bit of an emotional roller coaster because I never thought that would be me or I'd ever look like that," she says.
As for this season of DWTS, it's probably no surprise that Osbourne is rooting for the underdog. "I love Bristol [Palin]," she says. "I think she's what the show is all about. She puts her heart into what she's doing; there's such vulnerability in her, and she gets up there every week by herself and does it."