By Breeanna Hare
(CNN) -- Matthew McConaughey lost 40 pounds for December's "Dallas Buyers Club," and Matt Damon worked out for four hours a day to get ripped for "Elysium."
Ashton Kutcher, meanwhile, wanted so badly to get the role of innovation icon Steve Jobs right, he put himself in the hospital.
The 35-year-old actor became a fruitarian while filming Steve Jobs biopic, "jOBS," in an attempt to "understand some of his discipline," Kutcher explained to CNN.
He picked up a book Jobs once read by Arnold Ehret called "Mucusless Diet Healing System" and began to eat nothing but fruit, shedding 15 to 18 pounds in the process, according to "jOBS" director Joshua Michael Stern.
"(Jobs) was a really disciplined guy in a lot of ways, around his work and his life and his relationships and his products," Kutcher said. "And part of going on the diet was just to try to get an understanding of that. I didn't like it very much. It was really painful, ultimately. But it was really worth it, 'cause I think I gained a level of empathy towards that kind of discipline and focus that I don't think I could have played the role without."
Arriving Friday, "jOBS" traces Steve Jobs' ascendance from college dropout to globally influential creator and will recount his founding of Apple along with Steve Wozniak (played by Josh Gad).
As one of the more tech-savvy stars in Hollywood, Kutcher was initially nervous to portray someone he calls his "hero."
"I admire him, and I admire his work," Kutcher told CNN. "The scariest thing for me was that I wanted ... people to see my portrayal of him and see it as a portrayal that was honoring him and being honest about some of the flaws that he had. That was really a daunting task."
Of course, Kutcher came to the part with a genetic advantage: The actor, who also stars on CBS' "Two and a Half Men," shares a resemblance to the late Jobs, who died in October 2011. But according to director Stern, Kutcher didn't try to rely on just his looks.
"Ashton walked into the first meeting already channeling Steve Jobs," he told CNN. "He had the mannerisms; he'd studied hundreds of hours. He knew from that first meeting that I needed to take away evidence that he could play the part."
Kutcher's total immersion into the character was so complete that Stern walked away from the actor with newfound respect. "He studied the guy; he lived in his skin every day, which wasn't the easiest place to live, and I really respect him quite a bit. He gave everything he had, and more than anything I knew that this role was important to him. And when something's important to you no matter what you do, you're going to give it everything you have."
Despite those efforts, "jOBS" has faced criticism ahead of its release date, from Kutcher's casting on down.
The biopic was originally slated to bow in April, but was bumped back to August reportedly so the studio could have a longer marketing push. Reviews, thus far, have been mixed, and then there are those questioning its timing.
Kutcher says that when he received the script, which was already a work in progress when Jobs died, that he did have that "immediate concern."
"I know that there were some people that were close to him who didn't want a movie to be made this soon," he said, but because "I have friends that actually know him, I felt ... I could at least protect his legacy somewhat by playing (the part), and I knew I would dedicate myself to making it as good as I could."
When you make as great of an impact on the world as Steve Jobs did, that story's going to be told eventually, no matter what. "I would rather have it get told before the tales about him get too tall and while we could tell an honest story," Kutcher continued. "A lot of times, someone passes away and all of a sudden the stories become these fictional tellings of what happened. I think this film is as close to true as we could find."
At this year's Teen Choice Awards, Kutcher addressed the young crowd in a Jobs-ian motivational moment. He told fans "sexy is smart," "opportunities look a whole lot like work" and closed his speech by saying, "build a life; don't live one."
CNN's Carolyn Sung and Jane Caffrey contributed to this report.
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