Keep in mind lots of actors do this for a living, they have personal trainers and meal dieticians who feed them and train them and make sure they stay in shape, get bigger/smaller to fit into the role they are playing.
Taylor Lautner gained over 30 lbs of muscle for his role for Twilight.
Show Image
(https://images-production.global.ssl.fastly.net/uploads/photos/file/230775/taylor-lautner-transformation.jpg?crop=top&fit=clip&h=500&w=698)
Edit: damnit now my work history has me browsing of pictures of taylor lautner.
's all over..
Tomorrow.. all them ghey rumors will pop up..
Then Toby is going to confess to you @ the cooler, anddddd all the office chix are going to be like wh000t.. from behind the glass some where..
Suddenly they all start talking to you and inviting you to go to the mall with them..
hahahahhahahahahaha