8. Renee Zellweger
Renee was asked to gain 20 lbs. to play her part as a "normal girl" in "Bridget Jones' Diary." By no means overweight, her chunkier frame lent more credibility to the part of a single 30-something in London. Problem? On the tail of BJD success, she was signed on to star as Roxie Hart in "Chicago" and what's a starlet to do? Oh, easily drop the 20 vanity pounds gained for a different movie role. It was done over the span of a few months and probably a lot and I mean a lot of jazz kicks.
7. Beyonce
When Beyonce snagged a part in the groundbreaking and Oscar award-winning "Dreamgirls," she needed to lose 20 lbs. fast. She turned to the "Master Cleanse," a diet where you consume nothing but a hot water, lemon, and maple syrup concoction for 10 days straight. If it sounds horrible, it's because it is. Critics have since spoken out against the Master Cleanse, pointing out that it's a totally unhealthy way to diet. What, starving yourself for 10 days isn't healthy? Who knew?