Jacked UP!

SWEATING IT OUT! THESE STARS PUT THE WORK IN TO GET RIPPED FOR THEIR ROLES - AND THEY'VE GOT THE SIX-PACKS TO PROVE IT!

KUMAIL NANJIANI

The Eternals star wanted to look the part to play Marvel's first South Asian superhero, so he enlisted trainers, nutritionists and even a cardiologist and hit the gym every day.

But the transformation from hot nerd to hunk tapped into the 45-year-old's insecurity about his body. "I know exactly what I weigh every day," he admitted in one interview.

"And if I could change something, I would love not to think about that."

ZAC EFRON

"In the best way possible, I did not look anything like me," the 36-year-old has said of bulking up to play 1980s pro wrestler Kevin Von Erich in The Iron Claw. "It was jarring at first." His costar Jeremy Allen White, who plays his wrestler brother Kerry Von Erich, was peeved at how seemingly easy it was for the High School Musical alum to get ripped.

"I had been training for months, lifting and doing this and doing that and eating more," he joked. "And I showed up, saw him, and I'm like, 'What is this even for? Why do I even try?"