In Tully, the 44-year-old plays mum-of-three Marlo who is gifted a night nurse while struggling to cope with the brutal reality of parenting.
"I gained close to 23 kilograms for this film," the 42-year-old 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. You know, it was a huge surprise to me. I got hit in the face pretty hard with depression. 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 had only three and a half months to gain the weight before filming commenced.
"The first three weeks are always fun because you're just like a kid in a candy store. So it was fun to go and have breakfast at In-N-Out and have two milkshakes," she said. "And then after three weeks, it's not fun anymore. Like, all of a sudden you're just done eating that amount and then it becomes a job. I remember having to set my alarm in the middle of the night in order to just maintain [the weight]."
"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 recalled. "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."
The mum-of-two said losing the weight again took around a year and a half and she described the process as “hell”.
"There's nothing fun about that… It was a long journey, very long journey," she said.
Particularly, she said, in comparison to her experience with transforming her body for her Oscar winning role in Monster.
"I was worried. I was like, this is taking a really long time," she said. "Because on Monster, I just didn't snack for five days and I was fine. 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. Like, you are 42, calm down, you're not dying, all good."