Are you trying to gain weight? This is what Colin Farrell did to gain 20kg in The Lobster movie

Farrell and co-star John C. Reilly had an exclusive chat with ET on Monday;  they opened up about how Farrell put on 45 pounds in just two months.


According to Reily, they just ate Haagen-Dazs or ice cream.

But how can you eat that much ice cream in a day without getting a freeze headache. And without missing a beat.

He was like, 'Oh, I just warm it up and just drink it. "In the microwave," Farrell added. "I was always a better drinker than an eater so I just applied that rule!"

Farrell, who said that the high-fat diet was only fun "for about two days," said that his health -- especially his sleep schedule -- suffered quite a bit.

Farrell revealed that it wasn't just eating melted 4,000-calorie meals that helped him put on weight -- he also refrained from exercising or really even moving at all.

Now, Farrell appears to be back in tip-top shape, and his method for losing all the extra pounds was apparently very straightforward: "I dropped the weight so quickly just by starving and working out," he explained.