Zac Efron - Efron Used Hudgens' Trainer For The Lucky One

The Hollywood hunk stars in the upcoming film adaptation of Nicholas Sparks' bestselling novel, about a Marine who searches for the woman he believes is his good luck charm, and Efron gained 25 pounds (11.3 kilograms) by regularly guzzling a chicken puree.

He also worked out with a keep-fit instructor to bulk up - and he had a personal connection to the exercise expert.

Efron tells ComingSoon.net, "Physically I started eating a lot. Eating through walls. Just eating and eating. That's all I'd do and I put on some weight that way.

"As far as the training goes, (I was) just trying different techniques and methods and working with a guy who I met who trained Vanessa during Sucker Punch... It's one of the only concrete things that you can do to feel differently about a character. I didn't feel like a Marine. I didn't have the posture. I didn't feel like I had the presence and that was just one thing for me that I could do to really up that change."

The High School Musical co-stars split in 2010.