The former Lost star adopted a whole new diet to lose some weight and he began working out rigorously with celebrity trainer Simon Waterson to achieve the scarily ripped body of his bad guy character Michael 'The Butcher' Sullivan.
He tells Eonline.com, "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."
But the strict diet restrictions and work-out regimes upset Fox's mum because he would no longer stop by for hearty homecooked meals.
He says, "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."
Fox has since been indulging in his favourite foods as he works to put the pounds he lost back on, but he is doing so very gradually and has only gained back 15 pounds (6.8 kilograms) of the 40 he lost.
He adds, "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."