Christian Bale in The Machinist (2004). (Photo: Instagram, @marekpayne)
Tom Hardy in Bronson (2008). (Photo: Instagram, @robyn_naisbett)
Natalie Portman in Black Swan (2010). (Photo: Instagram, @gael4469)
Christian Bale in Batman Begins (2005). (Photo: Instagram, @fdo___7)
Jake Gyllenhaal in Prince of Persia: The Sands of Time (2010). (Photo: Instagram, @tales.to.remember)
Christian Bale in American Hustle (2013). (Photo: Instagram, @merrickrwe)
Tom Hardy in The Dark Knight Rises (2012). (Photo: Instagram, @cinephilecommunity)
Matt Damon in Invictus (2009). (Photo: Instagram, @chrisalit)
Matt Damon in The Informant (2009). (Photo: Instagram, @matt.damon.fan.1200)
Tom Hardy in Warrior (2011). (Photo: Instagram, @matthieujsd)
Tom Hanks in Castaway (2000). (Photo: Instagram, @cinema_ketab)
Hugh Jackman in Les Misrables (2012). (Photo: Instagram, @peter_lakanen)
Hugh Jackman in The Wolverine (2013). (Photo: Instagram, @theplumsoldier)
Russell Crowe in Body of Lies (2008). (Photo: Instagram, @faith.hope.glory)
Matthew McConaughey in Dallas Buyers Club (2013). (Photo: Instagram, @filmbazz13)
50 Cent in All Things Fall Apart (2011). (Photo: Instagram, @filmcosk)
Charlize Theron in Monster (2003). (Photo: Instagram, @farzadmonfared1)
Robert De Niro in Taxi Driver (1976). (Photo: Instagram, @tippy_duz_it)
Robert De Niro in Raging Bull (1980). (Photo: Instagram, @moviefilms)
The actors in this list go to extreme lengths to turn into the characters they portray in films. Most doctors will not recommend extreme short-term body transformations like these, but not everyone gets paid millions to do it.