Mila Kunis says it took her just "hours" to regain the weight she lost for new movie 'The Black Swan'.

The actress - who stars alongside Natalie Portman in the Darren Aronofsky-directed project - lost 20lbs for role as a ballerina and while it took her a while to shed the weight, it didn't take her much time to pile it back on.

She said: "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.

"Going back to my poor eating habits, after having really good eating habits, my stomach was a little unsettled, but after production ended, the first thing I did was go and get Panda Express at the airport terminal and then, I landed in Los Angeles, 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. It was so good."