Kelly Osbourne Kelly Osbourne

Kelly Osbourne says being called fat broke her heart.

"It sets you up to hate yourself in a huge way. I truly believe it's the main reason I turned to Vicodin and ended up in rehab three times. I just hated myself," the 26-year-old tells Self magazine.

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Osbourne, who graces the cover of the December issue in a skimpy red two-piece, says that treatment for drugs led to weight gain. She says it wasn't until she competed on Dancing with the Stars last fall — where she finished third — that she realized she had been replacing the drugs with fatty foods.

Kelly Osbourne: "I would rather be called ugly than be called fat!"

After losing 20 pounds while on Dancing and another 30 pounds afterward, Osbourne says she's finally learned how to eat and exercise right.

"I never thought in a million years I'd be that healthy girl who wakes up every morning to exercise," she says. "After being called 'cherubic and chubby,' I'm rocking a bikini!"