But fear not that he's going down the destructive path taken by other teen icons -- it's all just part of the job.
For his role as a transsexual with AIDS in "The Dallas Buyers Club," Leto pushed his body through a brutal transformation.
"I waxed my entire body, including my eyebrows," he told reporters at the awards ceremony. "I've lost a lot of weight because I'm playing a young person with AIDS. It's been challenging but really inspiring, too."This isn't the first time Leto's changed his body for a role. For 2008's "Chapter 27," Leto gained 27 kilograms to play Mark David Chapman, John Lennon's murderer.
For "Dallas Buyers Club," Leto's co-star, Matthew McConaughey, also went on a punishing diet to lose 17 kilograms.
"I feel good, now," McConaughey said. "Overall, probably got 35 percent less energy. The tough part -- there have been plateaus."
"I haven't eaten in 21 days," Leto told the award ceremony's host, Mike Birbiglia.
All that waxing and primping (not to mention having to wear heels) has opened Leto's eyes to what many women endure on a daily basis.
"It's a lot of work to be a pretty little girl," he said. "I have a newfound respect for women in general."
The tough physical effort is well worth it for Leto, who loved the "beautifully written" script for "The Dallas Buyers Club" enough to make it his first movie in five years.
"I just immersed myself in their culture and the people and I hope I can represent them as honourably as possible," he said.
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Kelly Woo writes for Yahoo! Movies