07/20/2012 04:16 pm ET | Updated Jul 21, 2012

Joseph Gordon-Levitt, Other Celebrities Who Have Gotten Buff

His recent GQ cover has made it clear: Joseph Gordon-Levitt is kinda jacked. The 31-year-old former "Third Rock from the Sun" kid has grown up to be a bona fide action star, debuting bulging biceps in the much-anticipated Christopher Nolan flick "Dark Knight Rises," which opens in theaters Friday, July 20.

But Gordon-Levitt isn't the only male celebrity to have undergone a transformation, onscreen and off. Check out our gallery of male stars who have gone from lean to mean, including Christian Bale, Mickey Rourke, Zac Efron and more.

Male Celebrities Who Have Gotten Buff