Robert Pattinson would have to make a ''lifestyle change'' if he wanted to do shirtless acting.

The British hunk is often asked to do scenes without his top on when he is filming but says he doesn't have the requisite muscles like his 'Twilight Saga' co-star Taylor Lautner and would need to put in some serious effort to get the actor's impressive six-pack.

He told Reveal magazine: ''I'd have to make a lifestyle change if I wanted to do shirtless acting. But it seems like every single actor in the world is going a 'Taylor Lautner' scene - it's crazy. They have a scene where they walk out with like a 12-pack. It's like, 'Really? You're playing a normal guy! That doesn't make any sense.' But that's a prerequisite of being an actor. Or you can get fat!''

Robert also revealed he and girlfriend and co-star Kristen Stewart passed the time on the epic shoot of 'The Twilight Saga: Breaking Dawn Parts 1 and 2' by training their dog Bear.

He said: ''We got a dog when we were filming 'Breaking Dawn' as there was a lot of waiting around. We were in Louisiana, so we spent time training him there.''