Taylor Lautner isn't a naturally strong guy, but his career depends on becoming brawny. Between the first and second Twilight films, his character grew into a powerful werewolf. That meant he needed to gain 30 pounds of muscle in a year. Which he did.
Think about that: Taylor Lautner used to be a 5'10", 140-pound, bony teenager, and now he's a rippled fitness animal. If he can overcome physical shortcomings, anyone can.
(Source: Men's Health)