14. Colin Farrell
The actor later admitted he only ate tins of tuna and drank diet sodas and black coffee, rounding up his daily intake to only 300 calories.
“For a short space of time, it was grand,” Farrell told The Sun, however, he also admitted that the routine soon got boring and he got fed up with the diet, so to speak.
This wasn’t the only time he went through some serious physical changes for the role. Farrell previously had to pump up some badass muscles to star in 2004 movie “Alexander.”