6,000 Calories, Coconut Milk Ice Cream, Dozens of Doughnuts: How Hollywood Gains Weight

Paltrow's trainer, Tracy Anderson, known for giving her clients "teeny, tiny" bodies, also had a hard time with the actress' weight gain.

"That was tough for me because we've worked so hard on her body," Anderson told New York City's WABC-TV. "She went down from six days a week of training to three, and she ate everything in sight. Fried chicken, mashed potatoes. They filmed in Nashville, so it's a good place to have some comfort food."

Despite all that, Paltrow's bulkier figure was barely discernable from her usual slim frame, and she shed the extra pounds without much effort.

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"It didn't take her very long to lose the weight," Anderson said. "It only took her a couple of weeks. It didn't want to be on her anyway. Extra weight isn't something that she owned."

Stars Pack Pounds for Parts

Hollywood's perpetually popular bachelor let his body balloon for 2005's "Syriana." Clooney chowed down on pasta to pack on 35 pounds for his starring role in the political thriller. At a press conference prior to the film's release, he revealed he wanted to bulk up.

"I'm instantly recognizable, so we wanted to change it," he said. "I'm sort of happy at the idea that people when they first see me in the movie, or when they first see the poster don't even know it's me. To me, that makes me proud."

Though Clooney's fuller figure may have contributed to his on-set back injury which required multiple surgeries, ultimately, his weight gain gambit paid off: in 2006, Clooney scored a best supporting actor Oscar for "Syriana."