The film is based on the true story of rodeo rider Ron Woodroof, portrayed by McConaughey, who discovers he is HIV-positive and has developed full-blown AIDS.
Doctors give him just 30 days to live, but Woodruff decides that isn't good enough and researches better drugs available south of the border. In the process, he becomes a hero outlaw, smuggling AIDS drugs into Texas from Mexico and dealing them to those who need treatment.
Six-foot-tall McConaughey dropped 38 pounds for the role, and as Woodruff weighs just 135.
"I just kinda dared myself" to lose the weight McConaughey said in a 2012 interview with Larry King. "I haven't been this light since I was in the ninth grade. I'm kind of looking at it as sort of a cleanse, it's a bit of a spiritual cleanse, mental cleanse."
Jared Leto, who plays an HIV-positive transsexual who becomes one of Woodruff's business partners, also dropped significant weight, losing about 30 pounds to appear on screen at just 116.