'The Fighter' and 'Black Swan' seem like strange bedfellows, but they have more in common than it initially seems. Respective stars Christian Bale and Natalie Portman are gathering plenty of critical attention for their strong performances, as well as the stunning changes both made to their bodies to fit their roles. However, while this is practically par for the course for Bale, Portman is much more the subject of concern and criticism for her performance.

For 'The Fighter,' Christian Bale dropped an alarming amount of weight to play former boxer Dicky Eklund -- not so he could be in top-notch shape for sparring but because Eklund was addicted to crack. Bale has modified his body this way in the past in both directions -- in 'The Machinist,' he looked even more skeletal, having dropped over 60 pounds for the role, and then the actor bounced back almost immediately for 'Batman Begins,' where he fills out every inch of his bat-suit with rippling muscle.

On the other end of the scale, so to speak, Natalie Portman also subjected herself to rigorous training and weight loss to play prima ballerina Nina Sayers in 'Black Swan.' Portman, a former dancer, went back to the barre with a vengeance for this role, which probably will pay off in an Oscar nomination at the very least. Both Portman and costar Mila Kunis lost 20 pounds off their petite frames to play ballerinas, and Portman put in hours of ballet training on top of other exercise regimens and eventually the choreography for the film's dance scenes as well to perfect her performance.