"I always felt like a goofy celery stick... I was a tiny twig, with short hair. Completely different to what Garth (Davis) changed me into," Patel, 26, told The Independent.
"Garth would say, 'We need to make you more alpha and get your facial hair growing.' So I moved differently, I felt differently in my clothes and all these kind of things."
Patel also opened up about some of the preparation he did for the role, including travelling around India.
"I wrote a piece in my diary about the word hero, because you know the Bollywood stars when they are in public in India people call them hero, so they would call out hero to me, and I'm like, I wrote this thing in my diary about feeling less like a hero than ever before...," he said.