"The moment I signed up for the movie, I wasn't possessing the physicality of a DJ," Zac told ET, explaining his motivation for slimming down. "They sit behind their computers and they are not, I guess, built. So I just started running every day."
While 10 pounds might not sound like a lot, it's a big life change for an actor who's known for his formidable physique.
"I am very motivated when I go for it," Zach said.