Christian Bale believes it his obsession with his art form that makes him a great actor.

The 43-year-old British star is known for his total commitment to his roles and is prepared to do anything to bring his characters to life.

For his portrayal of insomniac Trevor Reznik in 'The Machinist' he lost 62 pounds reducing his body mass to just 120 pounds, whilst for his acclaimed performances as Batman in 'The Dark Knight' trilogy he built up his muscle and physique to be the Gotham City saviour.

For his next role as former US Vice President Dick Cheney in Adam McKay's upcoming biopic 'Backseat' he has gained a significant amount of weight.

Bale doesn't worry about the long-term effects his body transformations have on him because he feels as though he's ''invincible'' and he believes it is his total commitment to his work which allows him to give such memorable performances.

Speaking to the Metro newspaper, he said: ''I keep thinking I'm invincible. I like obsession. I hope that it stays as healthy obsession.

''There's just always been an image which struck me incredibly. Jimi Hendrix playing guitar, eyes closed, looking like he's in ecstasy, creating beautiful music ... and I don't know if I imagined the blood or not but blood flowing from his fingers. I don't care if it really happened or not but the point for me is that he completely ignores the pain because of the ecstasy. I enjoy that level of obsession and think that viewers deserve performers to take it to that level if necessary.''

'Backseat' will show Bale as Republican politician Cheney - who was the 46th Vice President of the United States from 2001 to 2009 - and it will follow his journey from when Cheney avoided military service in the Vietnam War, his rise to CEO of the multinational corporation Halliburton and finally becoming one of the most powerful and influential vice presidents to ever hold office.

His actions are considered to have led America into the Iraq War in the wake of the 9/11 terrorist attack in 2001.

As well as his impressive political career many will remember Cheney for accidentally shooting Texas attorney Harry Whittington during a hunting trip.

Sam Rockwell is to play former US President George W. Bush, Steve Carell is playing Donald Rumsfeld, the Secretary of Defence under President Bush whom Cheney served under, and Amy Adams as the Vice President's wife Lynne Cheney.