Jake Gyllenhaal doesn't believe transforming his body for roles has anything to do with acting.

The 36-year-old star has made major alterations to his appearance for several movies, including slimming down his physique for 2014's Nightcrawler and bulking up for 2015 boxing movie Southpaw.

While some actors may find changing their physique informs their performance, Jake insists this hasn't been the case in his experience.

"No, I don't think transforming your body physically has anything to do with the craft of acting," he told The Guardian, going on to add that the understanding of human behaviour is a technique to be learned and discovered. "My favourite actors are like artists, and when you see their career, you see someone who is able to actually physically draw a perfect figure and then deconstruct it, or not, based on a foundation of skill or practice."

The actor points to his upcoming film Stronger as one of his most challenging roles to date. In the movie, he plays Jeff Bauman, a man who lost his legs in the Boston Marathon bombing in 2013, and describes the struggles he faces as he adjusts to his new life.

"Although no matter how far you push yourself, to understand even the idea of that is almost close to impossible," he shared of playing Jeff.

Jake's next big movie is Life, a science fiction film directed by Daniel Espinosa, which also stars Rebecca Ferguson and Ryan Reynolds. The film follows a six-member crew of the International Space Station that uncovers what initially seems to be the first evidence of life on Mars, and Jake admits that part of the reason he was interested in playing the character of Dr. David Jordan was the scale of the production.

"After playing role after role where I've given a tonne of time in preparation, I made a resolution to just enjoy myself making a big, fun movie," he said.