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Charlize Theron really sunk her teeth into her latest role.

The actress says she put on nearly 50 pounds to play Marlo — an overwhelmed mother of three — in "Tully" by radically changing her diet.

"For the first time in my life I was eating so much processed foods and I drank way too much sugar," Theron told Entertainment Tonight.

"I just I wanted to feel what this woman felt, and I think that was a way for me to get closer to her and get into that mindset," she explained." You know, it was a huge surprise to me. I got hit in the face pretty hard with depression."

In the film out May 4, Theron's character and her husband turn to a nanny as they attempt to balance raising three young kids with their lives.

Theron said she only enjoyed indulging in the unhealthy foods for about three weeks before it started to lose its luster.

"I would literally wake up at two in the morning and I'd have a cup of cold macaroni and cheese just next to me," Theron told ET. "I would wake up and I would just eat it...I would just, like, shove it in my throat. It's hard to maintain that weight."

It took about a year and a half for Theron, 42, to ultimately lose the weight she put on for the role.

She'd previously gained weight for her 2003 film "Monster" — a performance that netted her an Oscar for Best Actress — but she notes it was easier to drop that extra poundage when she was 27 than it was this time around.

"It was a long journey, very long journey," Theron said of losing the weight this time. "And it's hard because I had press junkets and movies around it and nobody knew that I had done it for this. And I think in the beginning everybody thought I was wearing, like, when the first photos came out, everyone (thought it) was, like, prosthetics."