The film "Alex Cross" follows a young homicide detective/psychologist (Tyler Perry) as he meets his match in a serial killer (Matthew Fox). The movie is adapted from the worldwide best-selling novels by James Patterson, and Fox trained vigorously to to achieve the scarily ripped body of his bad guy character Michael "The Butcher" Sullivan.

The actor looks like a mean and lean thug with a shaven head, tattoos and veiny muscles covering his body.

The former "Lost" star adopted a whole new diet to lose a staggering 40 pounds. He also worked out rigorously with celebrity trainer Simon Waterson.

The actor told, "We worked really hard on this for five months. The training sessions were mostly circuit training. You're going non-stop from exercise to exercise, never taking any breaks for about an hour-and-a-half. I was burning a lot of calories and working on certain muscle groups. It was very strategic on his (Waterson's) part and very gradual."

Unfortunately, his strict routine didn't allow him to eat his mother's homecooked meals. "My mother hated it. She's Italian and she's a fantastic cook and loves to feed her son more than anything. She couldn't stand it. It really upset her," he added.

Since filming wrapped, Fox has only gained back 15 pounds. He explained, "I'm taking my time to put it back on but eating all the things I love to eat. I have a terrible sweet tooth. All those pies, ice cream and cookies were completely out the window when I was training. Pasta and bread were pretty much non-existent in the diet as well."