See which stars went from scrawny to brawny
For his role as a vampire killer in Blade: Trinity, Scarlett Johansson's ex gained 20 pounds of muscle and lost a third of his body fat. He told Men's Health he has to do exercise he'll enjoy. "If you hate your workout, you're not going to do it."
Credit: Jeff Kravitz/FilmMagic; Everett Collection