The funnyman, 51, forgoes a shirt in several of the film's scenes, showing off his svelte physique – which the actor credited to a strict diet.
"It's not a happy place to be," Carrey told PEOPLE at the movie's junket in Las Vegas on Saturday. "I'm back now. I've got Mr. Cuddly back and we're happy," he added while rubbing his stomach.
He continued, "It's not a natural place to live in that kind of shape," he said. "It looks great. It's fantastic and gets a lot of attention, but you have to eat, like, antimatter to stay in that kind of shape."
Although part of playing street magician Steve Gray involved gratuitous shirtless scenes, Carrey says he'd rather leave it up to the professionals.
"I figured that was Matthew McConaughey's thing," he joked.