11/02/2011 12:02 pm ET | Updated Jan 02, 2012

Leonardo Dicaprio Talks 'J. Edgar,' Dustin Lance Black Says He Got Fat

Whether he plays an underground cop on the streets of Boston or a wealthy aviation pioneer, true Leonardo DiCaprio fans will almost always see the dreamy boy from Chippewa Falls. But in "J. Edgar," where he stars as the not-so-sexy FBI director, his physical transformation is undeniably shocking.

The New York Times profiled the actor and revealed that while he spends a good deal of his time dating the most beautiful women in the world, he takes his work very seriously.

He did months of research to take on the challenging role. He toured the Justice Department and one of Hoover's past homes; he even found obscure film footage of a young Hoover and read through transcripts of his Congressional testimony.

"I wanted him to tell me how he walked, how he talked, what his hands looked like, what his desk looked like, what was above his desk," DiCaprio said."The research of these roles is half the fun and half the challenge -- maybe more. It's what makes it exciting to me."

While the actor studied Hoover's style and the way he spoke, he also picked up a little habit that made embodying his physique a bit easier, too: Eating.

Screenwriter Dustin Lance Black talked about DiCaprio's love of German chocolate cupcakes. "Some of those pounds on later Hoover were not prosthetic," he said. "I'll say it. Leo got a little fat."