British heart-throb Robert Pattinson's weight plummeted as he filmed vampire movie Twilight - because he virtually lived in the gym.

The Brit star put himself on a punishing exercise regime during filming, sometimes working out for five hours a day.

And it was only after intervention from the film's director that Pattinson realised he was overdoing it.

He tells Entertainment Weekly, "I used to go to the gym for about five hours a day but then I started losing so such weight. My head started to look really huge in comparison to the rest of my body.

"(Director Catherine Hardwicke) came up to me and said, 'What are you doing to yourself?'. (To gain weight,) I literally stopped exercising. Eating a cheeseburger after two-and-a-half months of doing that - it tasted like ambrosia."