Showing off his ripped bod, the "Savages" star chatted about his recent visits to the gym and working out with his wife, filmmaker Sam Taylor-Wood.
Check out a few highlights from Mr. Johnson's Q&A session below. For more, be sure to visit Men's Health UK!
On becoming a gym newbie:
"Only recently have I been introduced to the gym and heavy weightlifting and things like that. Before that, when I grew up, I just did a lot of gymnastics and dance. I had more of an athletic background but nothing where I was in the gym or using any kind of weights."
On his superhero training:
"Throughout the movie he's still got to be a weedy kid from high school so I couldn't have anything too dramatic. It had to be a reveal at the end. We got around that by wearing a lot baggier clothes. I'd put on weight and then I'd drop weight the minute I'm on set. That was the hardest thing, to maintain what you'd built up."
"You do become a bit reliant on working out. I feel a bit jittery otherwise. Or you've got to go run it off. It's good, that's another, it really motivated me to be in shape and keep healthy. You think about what you're eating. But not too much: I'm eating pancakes and donuts right now. Everything in moderation."
On staying fit with Sam:
"My wife does yoga and I do yoga also. Although I find the two don't go together, you can't just smash up heavy weights and do yoga otherwise you find you can barely put your hands behind your back."