Charlize Theron Gained So Much Weight For Her 'Tully' Role That Her Daughter Thought She Was Pregnant

Charlize Theron's role in Tully required her to wake up and eat macaroni and cheese in the middle of the night. However, the actress told Entertainment Tonight that getting paid to stuff her face with the tasty cheese dish and other junk food was far from a dream job.

According to 42-year-old Theron, she gained around 50 pounds to play an overwhelmed mother of two named Marlo in the movie Tully, Juno team Diablo Cody and Jason Reitman's latest collaboration. The actress explained that she felt like changing the shape of her body by changing her eating habits would really help her connect to her character, but the side effects of binge-eating sugar and fast food were rather unpleasant. Her unhealthy new diet put her in a bad state of mind, and those around her also suffered due to her altered attitude.

"You know, it was a huge surprise to me. I got hit in the face pretty hard with depression," Theron said. "Yeah, for the first time in my life I was eating so much processed foods and I drank way too much sugar. I was not that fun to be around on this film."

Charlize Theron admitted that eating at In-N-Out for breakfast and downing two milkshakes was fun at first, but things began changing when she was about three weeks into her fast-food diet. Stuffing her face started to feel like a chore, and it became so difficult to maintain the weight she had already gained that she had to set her alarm so that she could wake up in the middle of the night and eat.

"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," she said. "I would wake up and I would just eat it...I would just, like, shove it in my throat."

Charlize Theron Had A Difficult Time Losing The Weight She Gained For 'Tully'
Getty Images | Matt Winkelmeyer

In addition to having a negative effect on her sense of well-being, the results of her drastic diet confused her two children, Jackson, 6, and August, 2. According to Charlize, her daughter thought that she was pregnant.

"My little one was convinced that I had a baby in my belly," she said.

Charlize Theron actually does play a pregnant woman in the movie Tully -- for a short period of time, at least. In the dramedy, her character enlists the aid of a "night nanny" (Mackenzie Davis) after she gives birth to her third child. According to the San Francisco Chronicle, the frazzled mom suffers from postpartum depression. She needs all the help she can get, but failing to be a supermom who can do it all for her kids causes her to struggle with feelings of inadequacy.

Speaking of being a supermom, Charlize had to juggle motherhood, press junkets, and workouts after she was finished filming Tully. She previously gained weight for her Oscar-winning role as serial killer Aileen Wuornos in the 2003 film Monster, but she said that all it took for her to lose that weight was skipping snacks for five days. When she didn't lose the 50 pounds as easily this time around, she panicked.

"You know your body at 27 is a little different than your body at 43, and my doctor made sure to make me very aware of that," Theron said. "Like, you are 42, calm down, you're not dying, all good."

Tully hits theaters May 4.