(CNN) -- It looks like 2013 is going to be the year of the severe physical transformations for actors.
For his upcoming project "Nightcrawler," Jake Gyllenhaal has not only grown his hair long enough to sport a "man bun," but he's also become remarkably thin.
"(I've lost) probably a little over 20 pounds so," Gyllenhaal told CNN at this week's Hollywood Film Awards. "I'm playing a character that is hungry literally and figuratively."
Written and directed by Dan Gilroy, "Nightcrawler" is a crime drama that stars Gyllenhaal as an ambitious young man who becomes enmeshed in Los Angeles' underground scene of crime journalism.
"He is very driven," Gyllenhaal says of his character, "and doesn't have very much time to think about anything (else). It's an amazing script."
The 32-year-old isn't the only star who felt the need to transform himself physically to get into character. "How I Met Your Mother" star Jason Segel has become almost unrecognizable after slimming down for the comedy "Sex Tape," and both Matthew McConaughey and Jared Leto became severely thin for "Dallas Buyers Club."
Not everyone loses weight for their characters though. In David O. Russell's anticipated December release, "American Hustle," Christian Bale -- already no stranger to transforming himself physically -- packed on some pounds.
CNN's KJ Matthews contributed to this report.