The 31-year-old actor plays the title role in 'Superman' - director James Gunn's new take on the comic book hero - and he has revealed he struggled to fit into his clothes after he gained weight to portray the Man of Steel.
During an appearance on the 'Manly Things (Sort Of)' podcast, Corenswet explained: "I wasn't 238 [pounds] when we started shooting. I was 238 at my max.
"It was so awesome, I wanna go back. I put on like one of those crew neck sweatshirts ... Champion. And I put on one of those sweatshirts - like an XL or double XL - and I was like, 'I fill this out. This is amazing'. I didn't fit into any of my pants."
The actor explained he actually lost weight before shooting started, adding: "That was at the peak of my bulk. And then I slowly lost weight before we started shooting. I started shooting at about 228, 230 ...
"I know I wanted this to be my excuse to see what it felt like to gain essentially as much weight as I could."
However, he admitted he "didn't feel great" at his heaviest because his body hadn't adjusted to carrying so much extra weight.
In the new film, Corenswet plays Superman/Clark Kent with Nicholas Hoult as villain Lex Luther.
It's due for release in July 2025, and director Gunn recently expressed his gratitude for the "journey" in an emotional message posted on Instagram.
Gunn wrote: "And that's a wrap. God bless our cast and crew whose commitment, creativity, and hard work have brought this project to life.
"I set out to make a movie about a good man in a world that isn't always so much. And the goodness and kindness and love I've encountered on a daily basis on the set has inspired me and thrust me forward when I felt too spent to move on my own. Thank you all from the bottom of my heart. It has been an honour."
The moviemaker added: "The destination has been 'Superman', but the journey has been the toil and the laughter and the emotions and ideas and magic we've shared together on set - and for that I am forever grateful."