Chris Hemsworth's Extreme Diet for Formula One Film 'Rush'
PHOTO: Chris Hemsworth in the movie Rush

Jaap Buitendijk/Universal Studios

To prepare for his latest role as a Formula One race car driver in the upcoming film "Rush," Chris Hemsworth had to shed 30 pounds of muscle.

"It was pretty brutal," he told The Hollywood Reporter. "I've said it before, but my wife [Elsa Pataky] was pregnant at the time and I had more symptoms of a pregnant woman than she did. I was moody and hungry all the time. I understood addiction for the first time, to be honest. I immediately knew what it is like to be truly at the mercy of something. Literally, food was the last thing I thought about before I went to bed and the first think I thought about when I woke up."

"I ate very little protein and carbohydrates. And then I'd just run to sweat it off," Hemsworth said.

Hemsworth plays the late James Hunt in the period action flick about the British bad boy's rivalry with Austrian Niki Lauda (played by German-Spanish actor Daniel Bruhl) for the 1976 F1 championship.

To fit in their cars, F1 racers typically measure between 5-foot-8 and 5-foot-11 and weigh between 150 and 160 pounds. The 6-foot-2-inch Hemsworth, who has famously played the muscled superhero Thor, got down to less than 190 pounds.

Check Out Other Stars' Extreme Diets

The 30-year-old Australian actor was actually shooting "The Avengers" in 2011 when he made his audition tape for "Rush."

"It came at the perfect time for me as far as the hunger and desire for what I wanted to do," Hemsworth told THR. "The story spoke to me on a few levels. However outrageous Hunt was, his willingness to stay true to himself and not conform to some standard or be packaged in a neat little box by the sponsors was intriguing. His message was, 'If I'm not having fun, what the hell is the point?' It's not a bad rule to live by."

While Hemsworth could relate to his character on many aspects, being a womanizer was not one of them.

"I would have to give a quick rebuttal if someone asked me if I had slept with 2,000 women like he did," said the father of 1-year-old daughter India Rose.

PHOTOS: Ups and Downs of Celebrity Weight

Hemsworth and Bruhl actually did their own driving during the grueling four-month shoot, though director Ron Howard put them in less-powerful Formula Three cars made to look like their faster counterparts.

Eventually both actors got up to speeds close to 100 mph.

"They are tricky things, like go-karts on steroids," Hemsworth told THR. "One of the mechanics said, 'You can't baby it. You have to drive it like you stole it.' That led to a few fishtails."

Asked if it was scary being behind the wheel, Hemsworth replied, "No, that was a hell of a lot of fun and not even work."

More ABC News