Kelly Osbourne shows off 50-pound weight loss on Shape cover

Kelly Osbourne has been flaunting her svelte new self for months, and she's finally opening up about the dramatic body change in bikini-clad photo shoot for the December 2010 issue of Shape.

In her interview with the magazine, the former "Dancing With the Stars" contestant credits a lot the change to her partner on the show, Louis van Amstel.

Osbourne says the diet and exercise regimen instilled in her 2009 turn on the series is one of the reasons why she's brought her total weight loss to 50 pounds.

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

Now a size 2, the 26-year-old is frank about her motivations to slim up. "I was called fat and ugly in the press almost my entire life," she says. "I understand that being judged by others comes with the territory, but it broke my heart and ruined my self esteem."

Well, nothing boosts your self esteem like wearing a bikini on a magazine cover.

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Photo credit: Shape