Christian Bale is Hollywood’s ultimate chameleon—especially when it comes to his physique.

The Academy Award-winning actor has put himself through all types of body transformations over the years, going from skinny (The Machinist), to fat (American Hustle), to superhero jacked (The Dark Knight trilogy).

But none of his previous transformations were quite like the one he did for Backseat, the Adam McKay-directed biopic of former Vice President Dick Cheney. For this role, Bale added more than 40lbs to his usually athletic frame, particularly his diesel neck. But what made it different was how he did it.

“I had never before gone to a doctor or a nutritionist about gaining or losing weight for my roles,” Bale told “But eventually that caught up with me. So, finally for Backseat, I decided that maybe somebody knows better than I do; so I went to somebody and they managed to get me up a good 40lbs. It’s never healthy to put on that amount of weight in a short amount of time, but I did it in the healthiest manner.”

Back in 2004, Bale dropped more than 60lbs to get into character as an insomniac for The Machinist, and he went to some extremes to get it done. “I came up with the absolutely brilliant method of just smoking cigarettes and drinking whiskey to lose weight,” Bale said. “But then when I tried it once again in my 40s, that didn’t work quite as well. I was waking up with heart palpitations and just not feeling right at all.”

Bale’s wife worried about the actor when he made the big change for that film.

“Of course she was concerned, but very supportive,” Bale said. “She threatened that if I did any permanent damage to myself, she would kill me. But she couldn’t help but feel somewhat guilty when she was eating dinner in front of me. She did lose some weight herself out of sympathy, I think. But I caught her a few times removing her hand from in front of my mouth as I was waking up; she was just testing for breath. But even though it was discomforting for her, she liked the character I played.”

Bale currently can be seen in the brutal Western movie Hostiles, playing an Army captain tasked with escorting a dying Cheyenne war chief and his family back to their tribal lands in 1892. Bale transformed for that role, too, but it was more about adding facial hair and an accent, and not so much transforming his body.

Backseat, co-starring Steve Carell, Alison Pill, Amy Adams, Sam Rockwell, and Bill Pullman, is expected to have a 2018 release.