When it comes to getting silver screen ready, it's not always about dieting.
In fact, for a handful of Hollywood's most successful female action stars, fitting the part meant bulking up—in the kitchen and at the gym.
Whether it was a boxing Hilary Swank in Million Dollar Baby or one-handed push-ups from Demi Moore's lieutenant-in-training for G.I. Jane, actresses have proven flexing their muscles can be beneficial on the big screen.
For Swank, getting in the ring meant her second Oscar. Eight years later, Jennifer Lawrence blazed onto the scene yielding a bow and arrow as Katniss Everdeen in The Hunger Games, a film that remained number one at the box office for four consecutive weekends and cemented Lawrence as a bonafide action hero.
However, the success of such roles is in many ways dependent on the physical. The body of a fighter in any form cannot be faked, so these actresses had to commit to transforming with the help of months of dedicated training and coordinated meal plans.
Still, the effects of such pursuits paid off far beyond the box office. In a genre typically reserved for male stars, these ladies proved they, too, could kick ass. "[My husband] started training more because I became so strong," Wonder Woman's Gal Gadot told E!'s Maria Menounos.
Furthermore, the powers of playing heroes on camera also helped them tackle their personal lives.
"I so needed to be Catwoman in that moment," Halle Berry told Oprah Winfrey in 2004 of her split from ex Eric Benét. "I so needed to take control of my life, make some tough life decisions for myself and putting on that suit made it a whole lot easier."
Visit E!'s gallery here to see some of the most famous female transformations—and how they did it behind the scenes.