By Piya Sinha-Roy
LOS ANGELES, Mar 2 (Reuters) - Jared Leto, the former teen heartthrob who left Hollywood to become a rock star, won the best supporting actor Oscar on Sunday in his return to movies as an HIV positive transgender woman in "Dallas Buyers Club."
Leto, 42, won over both critics and audiences with his portrayal of Rayon in the 1980s era AIDS drama, and was seen as favorite for the supporting actor Oscar. He beat out Bradley Cooper, Barkhad Abdi, Jonah Hill and Michael Fassbender.
The blue-eyed Leto, who rose to fame as a troubled teen in the 1990s TV series "My So-Called Life," has forged a career of complex roles. He played a heroin addict in 2000's "Requiem for a Dream" and a 118-year-old man in the 2009 independent sci-fi film "Mr. Nobody."
The actor then stepped away from film to focus on being the frontman of alternative rock band 30 Seconds to Mars.
But it was Leto's return to film in "Dallas Buyers Club" that piqued the interest of audiences, especially as the actor documented a weight loss of 30 to 40 lbs (13-18 kg) to transform himself into HIV-positive character Rayon.
"This is for the 36 million people out there who have lost the battle to AIDS," Leto said as he accepted the Oscar.
"To those of you who have felt injustice because of who you love and who you are, I stand here with you and for you."
"Dallas Buyers Club" is based on the true story of homophobic drug addict Ron Woodroof, played by Matthew McConaughey, who smuggles much needed but unapproved medication into the United States to distribute to other AIDS patients. He forms an unlikely friendship and alliance with the sweet and tolerant Rayon.
The film earned six Oscar nominations including best actor for McConaughey and best picture.
Leto, who has been touted for his edgy style on the red carpet, has been juggling his music with his duties on the awards circuit where he was won best supporting actor trophies at the Golden Globes and the Screen Actors Guild awards.
The actor took a break from his band's world tour to attend the Oscars on Sunday with his mother Constance as his date.
During his acceptance speech, Leto recognized two places struggling with violent social unrest.
"To all the dreamers out there around the world watching this tonight, in places like the Ukraine and Venezuela, I want to say 'we are here'," Leto said. "And as you struggle to make your dreams happen, to live the impossible, we're thinking of you tonight."
Leto charmed the media backstage, handing his Oscar to the crowd and urging them to take photos with it. "Does anybody what to try it out for size?" he said, handing it to reporters who passed it around as he answered questions.
"If you have swine flu, please don't touch!" he joked. "I bet this is the first person to ever give their Oscar away for an orgy in the press room."