June 25, 2012 12:00 PM

Joe Manganiello

Getting in shape to play a werewolf on True Blood is so intense-he works out twice a day, focusing on different body parts, six days a week-that the actor, 35, didn’t even need to diet for Mike. “I ate a ton,” he admits.

Does cardio on an empty stomach for maximum results.

Alex Pettyfer

Cardio and weights five times a week helped the former “couch potato,” 22, bulk up. But the film’s rigorous dancing made the biggest impact. “The coordination involved was much harder than hitting the gym,” he says.

Packed on 15 lbs. of muscle.

Matthew McConaughey

“You wanna see a guy really get into shape?” asks the Texan, 42. “Tell him he’s going to be stripping on a 40-ft. screen.” With just 10 days to prepare, he ate five meals of only protein and worked out twice a day.

Bought the cast cheeseburgers and fries at the end of the shoot.

Channing Tatum

Tatum, 32 (a former exotic dancer), lifted weights and did cardio for three hours a day and followed a strict dairy- and gluten-free diet. The result? He had “under 5 percent body fat,” says nutritionist Phil Goglia.

Snacked on almonds and cherry tomatoes.

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