Kristen Stewart told Total Film magazine: "The cool thing is that it's not just physical. You can read it all over him, just in his entire attitude. The difference between the kid that did 'Twilight' and this guy now is pretty astounding."
While Taylor, 17, admits it was a struggle for him to get in shape for the highly-anticipated follow-up.
He said: "When I was filming 'Twilight', I knew that Jacob's character changed a lot so if I wanted to continue portraying him correctly, I had a lot of work ahead. So I started hitting the gym. I got a personal trainer. I started eating a lot of food and cut the sugars. It was a lot of work, but it was definitely worth it."