Check out Kelly Osbourne's bikini body!

The formerly size-14 star, 26 -- who has opened up to Us Weekly before about her new svelte shape -- poses on the cover of December's Shape in an L*Space bikini.

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"I've never worn a bikini in my whole life," says Osbourne, who tells the magazine she's shed 50 lbs over the past year, USA Today reports. "I was called fat and ugly in the press almost my entire life.

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"...I understand that being judged by others comes with the territory, but it broke my heart and ruined my self-esteem," says the 5-foot-2 star, who now weighs 112 lbs. "It sets you up to hate yourself in a huge way. I was so angry about the things people said about me."

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The harsh criticism is one the main reasons she turned to Vicodin "and ended up in rehab three times," she says. "I just hated myself."

Her 2009 stint on ABC's Dancing With the Stars not only improved her confidence -- but also her eating habits. Her dance partner Louis van Amstel taught her how to eat healthy. and encouraged her to exercise regularly.

"He made me eat turkey burgers and salads and explained to me that a high-protein, low-carb diet would keep me energized," she says. "Then I started losing weight and realized, 'Oh, it's true what they say: Diet and exercise really work!'"

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