While interviewing for the September issue of Esquire, Pratt said he originally rejected the role because he didn't picture himself as an interstellar adventurer.
"I didn't want to go and embarrass myself like I did when I auditioned for G.I. Joe a couple of years previously," said the Parks and Recreation actor. "I went in there, and halfway through I saw the director's eyes just glaze over. It made sense -- I was a little heavy and out of shape. I was not gonna play someone from G.I. Joe. I did not look like a G.I. Joe action figure come to life."
In the end Pratt was able to get into superhero shape and can now do "40-inch box jumps" and all kinds of "action-hero physical stuff."
"Jumping that high feels really good. You see a giant hillside, and you think, I wanna get up that. You see a building, you think, I could climb that. When you get in shape, the world around you becomes things you wanna jump on and climb up," the actor told the magazine.
While his wife Anna Faris has said she wishes Pratt would go back to his old size, the actor might want to keep the work out routine alive for a little longer as he'll have to reprise his role in the upcoming Guardians of The Galaxy sequel, which is expected in theaters in 2017.
The September issue of Esquire is on stands now.