Matthew McConaughey talks about the unexpected side effects of his drastic weight loss for his Oscar-nominated role as an Aids patient in Dallas Buyers Club.
When Texan rodeo-riding electrician Ron Woodroof was diagnosed with HIV in 1985, aged 35, he was given 30 days to live.
He died seven years later, due to complications from Aids, in September 1992.
"Through pure rage and by any means necessary this guy did what he had to do to self-preserve and stay alive," says Matthew McConaughey, who shed nearly 3st 7lb (47lb; 21kg) to play Woodroof in Dallas Buyers Club.
"He broke the law, he smuggled things in and he became basically a black-market drug dealer."
The film, directed by Jean-Marc Vallee, is based on Woodroof's real-life experiences. In the month before his death, Woodroof told screenwriter Craig Borten his story for a film that would ultimately take almost 20 years to get made.
Dallas Buyers Club refers to the private members' group that Woodroof and fellow Aids patient Rayon, an invented transgender character played by Jared Leto, established in order to provide alternative - and unauthorised - treatments sourced from abroad. The club was the subject of frequent raids by the police and Food and Drug Administration (FDA).
"Ron didn't find a magic cure that kept people alive," says McConaughey. "The drugs that he was selling were keeping people alive longer and they were having healthier lifestyles while they were alive."
Both McConaughey and Leto are up for Oscars and considered to be frontrunners in their respective categories (best actor and best supporting actor).
Much attention has focused on the huge amount of weight that both actors lost for their roles. McConaughey "chewed a lot of ice" while he got himself down to 10 stone for the majority of the shoot.
"I did it in as healthy a way as I found possible," he says.
"I met with a nutritionist. I gave myself four months to lose the weight. I had my programmed meals, lost 3.5lb a week - like clockwork - and got down to my desired weight, which turned out to be 47lb lighter."
Were there any unexpected side effects?
"The surprise was how the energy that I lost from the neck down transferred to the neck up. I became clinically aware, almost hyper, I needed three hours less sleep a night.
"I had an amazing amount of energy from the head up. That was something I didn't know was going to happen."
According to McConaughey, a similar thing had happened to Ron. "His body was withering away, but from the neck up he was like a starving baby eagle - and he was just savagely clinging to life. He was literally, and figuratively, hungry."
To help him get into character, McConaughey had access to Borten's taped interviews with Woodroof. "He would sound like a medical expert or a scientist, and then he would slip in a conspiracy theory and then he would tell a joke, and then lose his train of thought."
The actor also met Woodroof's family, who allowed him to read Ron's diary from pre-1985.
"There was the man alone on Saturday night before he had HIV, and that was my secret weapon. That gave me the monologue so I could go and have the dialogue [in the film].
"His family was very honest with me about who he was. They didn't try to sugar-coat this man."
With this year's Oscars under a month away, McConaughey - along with actress Amy Adams - is in the unusual position of appearing in two films up for best picture.
As well as Dallas Buyers Club he has a scene-stealing turn as a chest-beating stockbroker in The Wolf of Wall Street. (Adams is in American Hustle and Her.)
How does he feel about his recent run of success? "Well, it feels great. I'm excited about it. I'm proud of the films I've been able to be in - from The Wolf of Wall Street to Mud to Dallas Buyers Club."
He calls it a "minor miracle" that Dallas Buyers Club got made at all. It was shot in 25 days for the relatively small budget of $4.9m. Nominated for six Oscars in total, it's already made more than $22m in the US.
"It's vital," says McConaughey, "it has translated, it has communicated with people, it's become personal with people. That's something I'm very proud of."
Dallas Buyers Club is out in the UK and Ireland on 7 February.