Jared Leto was a little out of breath when he got on the phone to talk to me this week about his movie "Chapter 27," which opens in limited release Friday.

I wondered if he was just back from a workout. After all, he'd gained 67 pounds to play John Lennon's killer, Mark David Chapman, in the movie.

"No, I'm leaving for Africa in a couple of hours," he said as he settled in for a chat.

Why Africa?

His alternative rock band, 30 Seconds to Mars, is playing shows in Capetown and Johannesburg. It's his first trip to the continent since making 2005's "Lord of War."

But Jared wanted to take some time to talk thoughtfully about "Chapter 27," a movie that required more of the 36-year-old actor than any previous role.

"What was interesting is it changed everything about who I was physically," he said of the weight gain. "It changed the way I walked, the way I talked - and even changed the way I laughed. It was essential to discover a different side of myself."

Now back to his trim self, Jared said he would never do something like that again to his body.

"When I was making ("Chapter 27"), I eventually had to go to the doctor. I was getting very, very ill. ... It was a very painful thing to do. Toward the end of shooting, I could barely walk without being in severe, severe pain."

While the dramatic weight gain was the most obvious part of his preparation for the role, the internal process was heavily involved.

"I was really trepidatious about taking on this part, for obvious reasons," he said. "Ultimately, I felt it was important to examine the failure of humanity, of the individual. ... This is a film about madness and obsession, about the darkest side of a person. I would hope when someone watches a film like this that it provokes questions."

"Chapter 27" focuses on Chapman's activities and the people he encountered during the three fateful days before the shooting. Among the people is a young fan played by Lindsay Lohan, who made the film before her scrapes with the law last year and her rehab stays.

"She was excited to do something drastically different than she had ever done before," Jared said. "We thought it was brave of her to take a chance and play a supporting part in a film that was so different."

Having watched the movie the night before, I remarked how eerie it was that it was filmed in front of The Dakota, the famous New York City apartment building where Lennon lived and where Chapman shot him.

"I didn't like it, to be honest," Jared admitted. "It's not something that you look forward to doing. The unfortunate thing is, it's such a landmark. It's like the White House. It's a character, a face of New York City. The filmmakers felt it important enough to have to do that. This is a very, very low-budget, experimental film, not a traditional Hollywood melodrama."

Jared plans to continue with his acting and music careers even if there is an occasional conflict, as happened when he had to turn down a role in the Clint Eastwood-directed "Flags of Our Fathers."

"I'm not an actor dreaming of singing on stage or in a band wishing I was a movie star," he said. "I love making films with a passion. ... Making music and touring the world is a tremendous gift. I am one of the luckiest persons on the planet to be able to do both."