From PEOPLE Magazine Click to enlarge
KELLAN LUTZ

"I'm running more, I swim a lot, and I box a lot," says Lutz, 26, who recently moved closer to the beach in L.A., where he enjoys doing shirtless outdoor workouts.



BOO BOO STEWART

The 17-year-old actor-singer and martial artist has a secret weapon in his quest to stay fit-his mom's a personal trainer.



TAYLOR LAUTNER

Lautner's trick for bulking up? "Eating thick, heavy food every two hours," he told USA Today. "That was really tough for me. Three protein shakes a day. Ugh."



ALEX MERAZ

When it comes to exercise, the guy who plays the volatile werewolf Paul has the heart of a beast. "He was intense," says Mariko Hammett, a personal trainer at Seattle's 24 Hour Fitness, who worked with Meraz, 26, while he was filming Breaking Dawn. "He's one of the most able clients I've ever had." Hammett would have Meraz do a range of exercises from shouldering 80-lb. sandbags to dragging tires. Says Hammett: "Alex's workouts were grueling. He was awesome."