The teenage actor altered his diet and upped his exercise regime to transform his slim physique into a buff build.
Lautner was allowed to eat anything and everything in preparation for the role, but he insists it wasn't as fun as it sounds.
He tells America's Star magazine, "Most people were like, that sounds amazing, to be able to eat all the time, and it is at first. But after a year and a half of it, I mean, I have to put something in my mouth every two hours, so it becomes kind of annoying!"