EXCLUSIVE: Matthew McConaughey Dishes on His Recent Birthday Festivities and Gaining Weight for 'Gold'

The star opened up to ET about his fun, outdoor b-day celebration and his physical transformation for his new role.

Matthew McConaughey just turned 47
and the Oscar-winning star says the festivities were a downhome family affair full of outdoor fun.

"My family took me down to South Texas and we camped out on the river that I learned to swim in, the Frio River," McConaughey told ET's Nischelle Turner at the Hollywood Film Awards in Los Angeles on Sunday. "It was cold but it didn't matter. We swam in that Frio River, took the rope swings all through the river all day.

"We barbecued outside and played music, my son DJ'ed, we cooked steaks and had a great time," he added.

WATCH: Matthew McConaughey Turns 47! 13 Times He Was Our Spirit Animal

A day after being honored as the birthday boy, McConaughey was in the spotlight once again at the Hollywood Film Awards, where he and the cast of his new film, Gold, were honored with the ensemble award.

In Gold, McConaughey plays Kenny Wells, a down-on-his-luck businessman whose fortune changes when he teams up with a geologist (Edgar Ramirez). Together, they discover a dense vein of gold deep in the Indonesian jungle.

WATCH: Matthew McConaughey Is Unrecognizable Sporting a Balding Head in 'Gold'

To play Wells, McConaughey underwent a physical transformation by putting on a quite a few pounds, and the actor revealed that he went about it the traditional way.

"Cheeseburgers and beer," he said. "And together, they work for putting on some pounds. It was a soft 217."

Check out the video below for a look at a bald, pudgy, treasure-hunting McConaughey in Gold, which hits theaters Dec. 25.