Not every shredded celebrity has always been shredded.

In fact, some of the most ripped guys in Hollywood started as skinny or even overweight. But when a big role comes along that requires some major changes, these guys are up for the task.

See the six-pack abs, bulging muscles, and major transformations from Hollywood leading men like Chris Pratt, Bradley Cooper, Jake Gyllenhaal, Jonah Hill, Christian Bale, and Tom Hardy, plus many more.

Here are 17 guys that transformed their physiques for the sake of their craft.