Lily James 'could barely recognize' Zac Efron on set of The Iron Claw

Zac Efron packed on the muscle to play a professional wrestler in The Iron Claw.

Efron stars in Sean Durkin’s intimate A24 drama, about the legendary Von Erich wrestling family and their rise to fame in the 1970s and ‘80s. To play the jacked Von Erichs, Efron and his on-screen brothers Jeremy Allen White, Stanley Simons, and Harris Dickinson spent weeks bulking up — to the point where they even astonished costar Lily James.

James stars as Pam, the future wife of Efron’s character Kevin Von Erich, and in an appearance on The Kelly Clarkson Show, the actress said she was shocked by just how brawny Efron got.

“I could barely recognize him!” James said. “There was so much more of him! I mean, he was huge! Those boys worked so hard. The wrestling you see in the film, it’s legit them doing it. I’ve never seen anything like it.”

Efron, White, Dickinson, and Simons spent weeks training to become professional wrestlers, prepping by getting in the ring with real-life experts. In EW’s recent cover story on The Iron Claw, the actors explained that they worked with the film’s wrestling consultant, Chavo Guerrero Jr., to practice everything from flying kicks to body slams.

Playing professional wrestlers also meant bulking up by consuming thousands of calories a day. Efron, of course, is no stranger to transforming for a role, especially after 2017’s Baywatch, but he told EW that The Iron Claw was a particular challenge. He ate “a large surplus of calories every day,” starting about six months before filming.  

“All the training was a way in for me, personally,” he added. “That’s what Kevin probably felt like and what these guys actually put themselves through because that’s how they really looked. It really was a way in for me, in a way I couldn’t have anticipated. It put me closer to Kevin. I think I became obsessed.”

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Related content:

• Into the ring: The Iron Claw stars talk dropkicks and their emotional wrestling drama
• Zac Efron and Jeremy Allen White transform into wrestling royalty in The Iron Claw trailer
• See all the photos from EW's Iron Claw cover shoot