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Featured Image Credit: Paramount Classics
Actors often have to go to seemingly pretty extreme lengths for roles - whether it's shaving all your locks off for Stranger Things like Millie Bobby Brown or putting on a few pounds to become much-loved spinster, as Renee Zellweger did every time a Bridget Jones flick cropped up.
But all that's a piece of cake compared to what Christian Bale had to go through for in preparation for The Machinist - the 2004 psychological thriller about Trevor Reznik, whose severe insomnia and psychological issues lead to an accident, which then leads him into a downward spiral of paranoia and delusion - when he had to shed 62 pounds.
Credit: Paramount Classics
Speaking to the Guardian, Bale explained that it wasn't the process of losing weight that was hardest - but the effect that it had on him physically and emotionally.
"It's an amazing experience doing that. When you're so skinny that you can hardly walk up a flight of stairs ... you're, like, this being of pure thought. It's like you've abandoned your body.
"That's the most Zen-like state I've ever been in my life. Two hours sleep, reading a book for 10 hours straight without stopping ... unbelievable. You couldn't rile me up. No rollercoaster of emotions.
"As soon as you start putting the food back in your stomach, the rollercoaster comes back."
Credit: Paramount Classics
He added that there was an 'easier way' to morph into roles, but he couldn't do it - instead needing to take himself to the extreme.
"I see actors who can just be themselves and then switch and give these really incredible performances, and then switch back to being themselves," he said.
"I find I start laughing because I'm too aware that it's still me. So I try to get as distant as possible. Otherwise, I can't do it."
He added: "It's helpful not to look like yourself. If I look in the mirror and go, 'Ah, that doesn't look like me' - that's helpful."
Credit: Warner Bros.
After The Machinist, Bale then had to get buff again - and quickly, as he had only six months to get suitably hench to portray Batman in Batman Begins.
To get into the caped crusader's costume quickly, Bale took on a high-protein diet and a regime involving heavy-core, plyometrics and resistance training.
He amazingly managed to pack on a whopping 100 pounds - only for director Christopher Nolan to tell him he'd got a too podgy, and ordered the actor to drop 20. You'd be fucking fuming, wouldn't you?
He also played Mark Walhberg's drug-addicted older half-brother Dicky Eklund in The Fighter, shedding the pounds big time to create an authentically emaciated aesthetic. But he won an Oscar for that one, meaning it was hopefully worth it in the end.
Now he's had yet another transformation, this time for playing stocky former Vice President Dick Cheney in an up-coming biopic.
The forthcoming film, titled Backseat, will explore the influence Dick Cheney had during the Bush administration, and his considerable role in American foreign policy following 9/11.