Mark Ruffalo says he 'force fed' himself to gain weight for new TV role

Mark Ruffalo has gone the way of Christian Bale and Matthew McConaughey in stacking on the pounds for his next role.

He's playing twins Dominic and Thomas Birdsey in an adaptation of Wally Lamb's novel I Know This Much Is True, which is becoming a mini-series for HBO.

And he's spoken out about how he's put on 30 pounds for the role.

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Speaking at the Television Critics' Association press tour event, he said: “When you’re force feeding yourself, some of the romance of food leaves.

“Those five weeks were kind of lonely. I’d been away from my family and (Thomas) hears voices, and I was imagining that life, and there was a couple weeks where I was just staying by myself, going down into the heart of this mental illness and studying it.”

Ruffalo had to gain weight to play Thomas – but not brother Dominic – who suffers from paranoid schizophrenia, his weight brought on as a side effect of his medication.

“There’s an element of mental illness in this project and you want to be as honest as you can to that, and it means a lot to me to be honest to that, which means going into that world and getting to know it and getting comfortable with it,” Ruffalo went on.

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“I was really afraid to play it, I think it’s a really an important issue and I want to tell it as honestly as possible, the responsibility of playing it was really apparent to me.”

The Avengers star is joined on the bill by Melissa Leo, who plays the twins' mother, Rosie O'Donnell, Imogen Poots, Juliette Lewis and Kathryn Hahn.

Written and directed by Derek Cianfrance, it will air in the US in April.