Known for his chameleon-like ability to completely immerse himself in a character, Christian Bale's transformation for The Machinist is legendary. To portray the emaciated insomniac Trevor Reznik, Bale lost a staggering 63 pounds, dropping his weight down to a mere 120 pounds.
Charlize Theron's portrayal of serial killer Aileen Wuornos in Monster earned her critical acclaim and an Academy Award for Best Actress. To fully embody the troubled character, Theron gained 30 pounds, wore prosthetic teeth, and underwent hours of makeup each day.
For his role as Ron Woodroof, a man diagnosed with AIDS, Matthew McConaughey shed an astonishing amount of weight. He lost around 47 pounds by following a strict diet and exercise regimen.
In "Cast Away," Tom Hanks portrays Chuck Noland, a FedEx executive stranded on a deserted island. To accurately depict Noland's physical deterioration over years of isolation, Hanks underwent a significant weight loss and grew out his hair and beard.
Known for his transformative roles, Jared Leto gained 67 pounds to portray Mark David Chapman, the man who assassinated John Lennon, in Chapter 27. The weight gain drastically altered Leto's appearance, and he consumed a diet consisting of pizza and melted Haagen-Dazs ice cream to achieve the desired effect.