Mirror, mirror on the wall, who’s got the sexiest Hollywood body of them all? "Extra" did some research, and we’ve found some incredible extreme makeovers and tons of hot bodies.

Jessica Simpson has had to go slim to squeeze into those tight daisy dukes for her new movie, "Dukes of Hazzard," and she did it with a ton of exercise ­ more than two hours a day, six days a week! "My husband thinks I’m a completely different person now," she told us.

And how is she keeping the pounds off? "I do watch what I eat," she insisted. "And I don't eat any sugar."

Gorgeous Kate Beckinsale went the other direction and actually added 20 pounds for her role as Ava Gardner in "The Aviator" -- to take off the pounds, she said she stopped eating the chocolate that helped her pack them on. "It was just fat Kate on the weekends and my jeans didn’t fit," she recalled, but said the no-chocolate rule got her back into mini-skirt shape.

Meanwhile, hot housewife Marcia Cross was ripped and camera-ready for her desperately exposing scene, when she showed up at her husband’s hotel room in red lingerie. "The wardrobe department keeps trying to give me smaller outfits," she told us.

And of course, Anna Nicole’s before and after continues to amaze the world.

But don’t think it's just a skinny sorority -- George Clooney is working on losing the more than 30 pounds he put on for his next movie, "Syriana." "I haven’t lost it all yet," he revealed to us. "I believe it's what's kept me off the Sexiest Man Alive list this year."

So if you need some inspiration, as we head into the holiday (that is the holiday meal) season, just look to the stars.