By StyleWatch
May 17, 2010 01:00 PM

Marion Curtis/Startraks

Showing up the body bullies who have railed against her curves in the blogosphere, Kelly Osbourne is now in the shape of her life–and reaping the high-fashion rewards of a sweat-till-you-drop gym regimen. “I never thought I’d wear a dress like this,” the Dancing With the Stars alum admitted to PEOPLE of the Matthew Williamson stunner she picked out for last Thursday’s Belvedere Pink Grapefruit Pop Up event in New York City, hosted by the designer to celebrate the limited edition caftan he created with the vodka brand. “I [usually] don’t like anything that shows my back. I’ve never worn a backless dress like this before…so I was really excited when I was putting it on.” Unlike some celebrity weight-loss winners, Kelly is frank about the hard work that went into dropping the pounds. “I’ve been working out with a personal trainer three times a week, which I really enjoy. It makes me think, ‘Why the hell did I not do this so long ago?'” Don’t expect to catch Kelly pumping iron in place of her mat and floor work, however. “I try to stay away from the machines,” she explains. “I find that machines will only work that one part of your body. And you’ll end up getting a really big muscle somewhere where you don’t want it.” And while she might not be reaching for French fries anymore as her go-to indulgence, “I don’t deny myself what I want, because…when I do [finally] get it, I’ll eat ten times more.”–Katherine Kluznik Rentmeester, Reporting by Jeffrey Slonim