How Brad Pitt Got His Hollywood Six Pack: 'He Really Takes His Workouts Seriously,' Says Source

Brad Pitt‘s most important scene in Once Upon a Time… in Hollywood may really come at the end of the movie, but there’s another midway through that has fans talking.

The moment finds Pitt’s character Cliff Booth on the roof of friend and actor Rick Dalton’s house trying to fix his antenna. Before he gets to work, Cliff decides to take off his shirt — revealing 55-year-old Pitt’s stellar physique underneath.

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Pitt’s six-pack abs are thanks to just one of the positive lifestyle changes the actor has made in recent years, sources tell PEOPLE in the most recent issue. The changes also included focusing on his diet and workout regimen — and the results are on full display in a scene reminiscent of his star-making six-pack moment in 1991’s Thelma & Louise.

He “really takes his workouts seriously,” one of the sources tells PEOPLE. “It’s been a whole lifestyle change. And he looks amazing.”

Once Upon a Time... in Hollywood | Sony Pictures
Once Upon a Time... in Hollywood | Sony Pictures
Thelma & Louise
Thelma & Louise

Since his 2016 split from Angelina Jolie, the actor has also “worked very hard on himself to be a better, healthier person and to be the best dad possible,” another source adds in the issue.

“These were always his priorities. That his career is going well is a happy bonus that he is thrilled about.”

The father of six recently helped celebrate Shiloh’s 13th birthday, and his oldest son Maddox, 18, will soon head to college in South Korea to study biochemistry. “Despite having help, Brad is a hands-on dad,” an industry insider says. “He comes from a close family, and he has continued to be a parent who is interested in the lives of his children.”