Once the go-to guy for fluffy romcoms, Matthew McConaughey is now one of the most exciting actors in Hollywood - with an Oscar nomination to boot. He tells Susan Griffin all about his toughest role to date.

It might only be February but it's already shaping up to be Matthew McConaughey's year. There's been his scene-stealing cameo in Martin Scorsese's The Wolf Of Wall Street, as well as a Golden Globe, a Screen Actors Guild Award and an Oscar nomination for his role as a homophobic Aids patient in Dallas Buyers Club.

It's been a whirl of red carpet events which, as glamorous as they are, can be long, drawn out affairs. Thankfully, he has his Dallas co-star and fellow Oscar nominee, Jared Leto, on hand with a few snacks. "Oh, he has bags of popcorn. He comes in with grocery bags of things so I've been partaking in a few of those," says McConaughey, grinning, and looking toned and tanned in jeans, a tight grey T-shirt and leather jacket.

He also lives by one rule - keep a clear head.

"I like wine but if I'm presenting, then I do it after that. I actually like to hit the stage without anything, but after that, I always have a glass," says the 44-year-old in his Texan drawl.

He'll want a clear head for the Academy Awards on March 2, as he's in with a strong chance of walking off with the golden statuette.

"I wasn't looking for a result but I did know when I read the script that this could be something special, and it's the kind of story that if we pulled it off, was something that could get recognition."

It's based on the true tale of Ron Woodroof, a man McConaughey describes as "a cantankerous b*****d with a wicked sense of humour".

"He's a guy who's easy to hate, yet you can't help but love him," he adds. "But when people are true to themselves like that, you realise, 'Man, that's just who he is', and you end up caring about him."

In 1985, Woodroof was diagnosed with HIV and given 30 days to live. The condition had already been ravaging the nation's gay community and Woodroof, a womanising, rodeo-riding electrician, was one of millions who saw Aids as "that gay disease".

Ostracised by friends and co-workers following his diagnosis, Woodroof was determined to survive and became a walking encyclopaedia of anti-viral meds, pharmaceutical trials, Food And Drug Administration (FDA) regulations and court decisions.

He not only survived for seven years but helped save lives by establishing a way in which HIV-positive people could access his alternative treatments - through the Dallas Buyers Club.

"Rage, that was what he was dealing with on every level," explains McConaughey. "I'm sure he was p***ed at God and he was p***ed at the FDA and that same emotion, which bore traits in him that some people found despicable, kept him alive for seven years. Rage is the emotion that gets more things done than any other. Like it or not, for good or bad, it causes action."

It's a tour-de-force performance, and one which required McConaughey, a sports fan often papped buffing up on the beach, to lose 47lbs.

"It was hard but, as an actor, to have something that you can give your full singular focus and commitment to for six months was wonderful," says the star, whose emaciated figure in the film makes him unrecognisable. "I never got complacent and that physical transformation and weight loss really structured my life, which helped me commit to what I needed to do."

He basically became a hermit. "I surrounded myself with everything Ron Woodroof, cancelled my social engagements, couldn't go out in the sunshine - and enjoyed every minute of it."

McConaughey credits his wife, the Brazilian model and designer Camila Alves, with whom he has three children under six, Levi, Vida and Livingston, for helping him through the process.

"I'm very fortunate, I have a highly supportive wife and family," he says. "Part of the support comes in insulating me so I can do the work I need to do and the other part, that's not expected, is when your wife's getting up with you at 4.30am. She doesn't need to do that and she's going, 'Go conquer', not just 'Have a nice day'. It's nice to have that support."

The film's producer, Robbie Brenner, always had McConaughey in mind for the role, saying: "Like Ron, he's from Dallas, he's handsome and he has a twinkle in the eye. Matthew also has intensity and intelligence like Ron did, mixed with that cowboy charisma and fighter's spirit. He was beyond perfect for the role."

McConaughey recalls his agent sending the script over to him. "I read it, I loved it and I remember saying, 'Make sure I stay attached to it, do not let me lose this'," recalls the actor, who rose to prominence in 1996's A Time To Kill, then spent the Noughties in romcoms before embarking on a new career phase with dark dramas like The Paperboy and Killer Joe.

"There are some scripts I get where I go, 'I like this' and then because I check in every six months, I might let one go if it's not sticking with me. This one stuck with me. It was incredibly human, with no sentimentality."

It would take another three years before the cameras started rolling and it "only became real eight or nine days before we started shooting".

Physical transformation aside, McConaughey prepared by listening to tapes of Woodroof, meeting with his family and reading his diaries. From this, he gained a new admiration for the man he'd be portraying on screen. "At the beginning of this journey he's a two-bit cowboy, and by the end of it, he's a damn scientist," states the actor, who wasn't interested in making "a message film" or a documentary about Aids. "This is a dramatic film about one man's life."

Having walked in Woodroof's shoes, he's contemplated what he would do in that situation - lay down and die, or fight for survival?

"I tell you, Ron Woodroof didn't regress and reassess," notes McConaughey. "I've not been in that position but instinctually and in my soul, I work from a life-affirming place, and I'm not going to go easy if I have a chance to fight for life."

Extra time - Matthew Mcconaughey

:: Matthew McConaughey was born on November 4, 1969, in Texas, USA, the youngest of three brothers. His mother, a teacher, and father, a gas station owner, divorced and remarried each other several times.

:: He spent a year in Australia before enrolling at the University of Texas, later changing his course from law to film.

:: Director Richard Linklater initially thought he was too good-looking for the 1993 high school movie Dazed And Confused, one of McConaughey's early roles.

:: He'll soon be appearing in TV crime drama show True Detective alongside Woody Harrelson but only agreed to do one series: "I needed it to be a finite amount of time and the writing was so good."

:: His next film's Interstellar alongside Anne Hathaway and Jessica Chastain, and directed by the "incredibly ambitious" Chris Nolan of The Dark Knight fame.

:: Dallas Buyers Club is released on Friday, February 7