Cutting weight—shedding pounds as fast as possible, often by forcibly sweating out excess water—is a common part of training montages. That's especially true for movies about boxers and wrestlers, both of whom compete in regimented weight classes. (There are some exceptions: In Silver Linings Playbook, directed by David O'Russell, the main character runs around in garbage bags. He's prepping for a dancing competition.) In O'Russell's other film, The Fighter, Micky Ward (played by Mark Wahlberg) wears a sweatsuit during aerobic exercises to get down to size. Both of these strategies are used in real life, but Holder says, "there are some inherent dangers such as dehydration and slight micronutrient issues if this [is] done [over a] prolonged [period]."