Prepping for Black Swan was not easy. Natalie Portman was among those in the cast asked to lose 20-pounds, Ironically, she recently did the exact opposite for Thor: Love and Thunder, asked to put some inches on her arms and appear more muscular. Now that's Hollywood for you...RELATED - Here's What Natalie Portman Went Through For Her Role In 'Black Swan'Along with Natalie Portman, Mila Kunis underwent the same type of stressful transformation. As if eating just above 1,000 calories wasn't hard enough, Kunis and company spent three months learning how to ballet dance, seven days a week.We'll take a look back at the preparation for the film and how Mila Kunis wasted no time indulging once production came to an end.

Mila Kunis Trained Seven Days A Week For Ballet Dancing Alone

The drama thriller Black Swan turned out to be a force both at the box office and critically. With Natalie Portman and Mila Kunis in the leads, the film made quite the chunk of change at the box office, worth $329 million. The film also thrived in terms of reviews, receiving an eight out of ten stars on IMDb and an approval rating of 85% on Rotten Tomatoes.

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It was a breakout role for Kunis on the big-screen, especially from a dramatic point of view. Even when she was cast for the role, Mila was so blown away by working alongside Darren Aronofsky, that she didn't even want to ask questions about her inclusion in the film.

The prep was not easy, however. Kunis had to face a couple of extremes, one of which, was learning how to ballet dance in just three months.

Although she pulled it off gracefully in the film, Kunis admitted alongside Collider, it was not an easy journey.

"It was far from effortless or sensual. It was three months of training beforehand. I was not a ballet dancer. You can only fake so much physicality, so you have to immerse yourself in this world, in the way that somebody walks, talks and handles themselves."

"So, it was three months of training, seven days a week, four or five hours a day, before production started, and then during production it was pretty much exactly the same."

Learning how to ballet dance was just one part of the journey, as Kunis was also asked to drop weight for role.

Mila Kunis' Diet Consisted Of Just Over 1,000 Calories Per Day

Speaking alongside Howard Stern, Mila Kunis admitted her diet for Black Swan wasn't the typical healthy low-carb, Hollywood type diet. Given that she was asked to eat 1,200 calories or less, Kunis needed to cut her cravings. That being said, she turned to cigarettes on the regular.

She told Howard Stern, "I had to look skinny in order to look like a ballerina. That’s how you fake it, unfortunately. I used to be a smoker, and so I smoked a lot of cigarettes and I ate a limited amount of calories. It was a 1200-or-less calorie diet a day… And I smoked. I don’t advocate this at all.”

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Kunis ended up losing 20-pounds for the role and that was evident on-screen when she was unveiled as Odile. However, once the project came to an end, Mila had no intention of keeping her new look. Instead, after the project ended, it was time to load back up on some fast food.

Mila Kunis Wasted No Time Hitting Up Fast Food Establishments Once The Film Came To An End

Kunis revealed that it took five months to lose 20 pounds and hilariously, it took really quick to gain it back.

"It took me five months to lose 20 pounds, and it took me hours to gain it back. It was magical, how quickly it all happened. Before production ended, the last time I had to do any sort of dancing, I ran home that night and had a massive bowl of mac and cheese. I was so excited."

Kunis admitted once the film wrapped up, it was time to really indulge. That all started at the airport and later, at more fast food establishments once she landed.

She told Collider, "The first thing I did was go and get Panda Express at the airport terminal, at Virgin America at JFK, and I was so excited. And then, I landed in L.A., got in my car, drove to In-N-Out and had a double-double, animal style with a root beer float, and it was fantastic. That is what I did. It was so good."

Clearly, Kunis had enough of the healthy foods.