"I'm breaking a sweat but I'm not going nuts," he says

John Goodman is no longer a couch potato.

“I know it sounds sappy, but it was a waste,” the 58-year-old actor tells PEOPLE. “It takes a lot of creative energy to sit on your ass and figure out what you’re going to eat next … I wanted to live life better.”

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Mission accomplished: The Treme actor has lost more than 100 lbs. thanks to his healthy new lifestyle. He quit drinking three years ago and hired Mackie Shilstone – a health coach who has trained many athletes including tennis player Serena Williams. Now Goodman has cut sugar from his diet and works out six days a week. “I’m breaking a sweat but I’m not going nuts,” he says.

He is excited about the results though, says Shilstone. “He remembers what it feels like to be extremely heavy and it’s something he doesn’t want again.”

Now, says Shilstone, “John is very agile. When I see him running I get out of the way! He can be a different type of actor now. He can take on athletic parts.”

Before Goodman becomes an action hero, though, he needs to focus on getting a new wardrobe. “I just ordered some nice slacks,” he says. “I finally got them and they’re too big now.”

For more on Goodman and other celebrity slim downs, pick up the latest issue of PEOPLE on newsstands now