Christian Bale
'The Machinist' (2004)
The actor made the decision to shed the pounds for his role as Trevor Reznik. He went from 13 stone to nine stone - and wanted to drop down to seven! But producers wouldn't allow him to transform any further fearing for his health.
According to reports he ate an apple and a can of tuna a day, and took up smoking to cut more calories. Fortunately he bulked up again in time for 2005's 'Batman Begins'.