Sebastian Stan used to be "so insecure" when he started his acting career.
The 37-year-old actor rocketed to fame after starring as Bucky Barnes in the Marvel Cinematic Universe (MCU) as part of the 'Captain America' franchise, and has said being around other actors with "massive" muscles made him feel insecure, and pushed him to train in the gym.
He said: "I was so insecure being around these massive f**king guys, so I started lifting really heavy and ate a lot. I remember I showed up, and I was a little bit bigger than I had been in 'The Winter Soldier'. The arm was a bit tight. I was losing circulation."
Sebastian used to compare himself to his co-stars Chris Evans and Chris Hemsworth, but has now come to terms with being "50 miles behind" them in terms of muscles.
He added: "I mean, next to Evans and Hemsworth and all those guys, I feel like I'm 50 miles behind. I don't think I can get to that size, to be honest. My body right now is probably the best it's ever been."
But the actor doesn't think his body matters when it comes to his acting, as long as his performance can impact people's lives.
Speaking to Men's Health magazine, he said: "All I know is that all movies affect people. I've certainly experienced first-hand many people who have been affected and helped by Marvel movies."
Meanwhile, the 'I, Tonya' star previously said shooting for the most recent Marvel ensemble movie 'Avengers: Endgame' had been "really hard".
He admitted: "It's not something you always deal with. I feel like you always kind of have a script. But I guess, what I would say is, because we've done these characters for a bit now, there's a little bit of a telepathic kind of knowledge between us and the writers. And you kind of can sometimes guess where they're going to take it, a little bit. For example, this one was really hard, because we keep going in and out. I go back there for a week, and then I leave for a month. And then I go back there for a few more days. So it's a little bit out of sync. But it still hopefully adds up in the end. Almost every scene is epic."