Whether he's bulking up for Batman or shedding weight for The Fighter, the British actor takes his roles pretty seriously.
However in a recent interview with The Sunday Times Culture magazine, Bale revealed his dedication has taken its toll.
"I can't keep doing it. I really can't," Bale explains.
"My mortality is staring me in the face.”
The Machinist in 2005 saw him at a dangerously low weight, dropping 25kg for the part, settling at just 54kg. In that same year, he stacked on 45kg for his character in Batman begins, almost unrecognisable.
In American Hustle and most recently VICE, Bale was forced to take an unhealthy route, admitting he ate "a whole lot of cheeseburgers" for the former role and "a lot of pies" to play Dick Cheney.
The American Psycho actor was also worried for his family.
"No matter what happens, my wife's seen it," he continued.
However, "my son loved the tummy. He would just bounce up and down on that a lot and headbutt it and bounce off it and fall to the floor."
It's always important to make sure your diet and exercise is consistent, and if you do find your weight yo-yo-ing, check-in with your GP.