Looks like Pauly D may have upset the delicate GTL balance.

During an appearance at the Hard Rock Hotel in Las Vegas this past weekend, the Jersey Shore star (real name: Paul DelVecchio) stepped out looking noticeably bigger.

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A source close to the DJ tells Us Weekly DelVecchio, 31, has put on some weight recently--but only because he's been logging extra hours at the gym.

"He's gained 20 pounds of muscle," the insider shares. "He is [exercising] nonstop . . .three times a day sometimes."

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Between his ramped-up workouts and his DJ gigs, DelVecchio has plenty to keep him busy these days. The Rhode Island native is also currently appearing in a Jersey Shore spinoff--The Pauly D Project--with his close friends Ryan Labbe, Gerard "Big Gerry" Gialanella, Jason "J-Rock" Craig and Michael "DJ Biggie" Morgan.

"The whole world, they know me from Jersey Shore. They know I can party in Jersey with some strangers that become my friends, but now with my show, you get to see where I came from, you get to meet my family, my friends, and see what it's like on a daily basis being a touring DJ," DelVecchio told Us last month about how his new series compares to the show that launched him to stardom.

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Added his pal Craig, "It's kind of like the pros. . . Seaside's like Little League."

This article originally appeared on Usmagazine.com: Jersey Shore's Pauly D Debuts Beefed-Up Look