Story highlights Matthew McConaughey underwent a dramatic physical transformation for his upcoming film, 'Gold'

The actor credits his weight gain to pizza, cheeseburgers and beer

McConaughey said his family didn't mind and nicknamed him 'Captain Fun'

(CNN) Matthew McConaughey is a pro when it comes to undergoing physical transformations for his film roles and in his latest movie "Gold," he's nearly unrecognizable.

The actor told an audience Monday night at a screening for the film that he gained 45 pounds to play businessman, Kenny Wells, who strikes gold in Indonesia.

"I was getting pretty damn fat as Kenny Wells," McConaughey said. "I was an all star in my family, nicknamed Captain Fun during that time because I was yes to pizza night, every night and it was cheeseburgers and beer."

McConaughey is no stranger to pushing the limits of his body. The actor lost more than 40 pounds for his role in the 2013 film, "Dallas Buyers Club." The performance won McConaughey an Oscar.

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