Tom Hanks
You may know him from his more physically demanding roles, but Tom Hanks has sacrificed his body many times for Hollywood's sake. He had to completely transform his physical form in order to look like he was actually starving while trapped on a desert island in Castaway.
WINSTON!!!
Hanks was tasked with putting on 50 pounds before the shooting for Castaway even began. After he put the weight on, he spent the next four months barely eating and working out for several hours out of the day to drop 55 pounds. This actually led to numerous mental and physical health problems that have followed Hanks for quite some time now.