It's a well known fact that appearance is a big deal in Hollywood.
But even though there are numerous good looking people walking around in the entertainment business, sometimes a casting director is looking for something a little bit different.
A number of stars have gone the extra mile and lost or gained quite a bit of weight for a particular part.
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Aussie movie hunk Chris Hemsworth is a great example when it comes to preparing for a role. For the movie In the Heart of the Sea, he sacrificed his usually buff physique and shed 33b in four weeks. The actor admitted that the experience was much more difficult than gaining the same amount for the Marvel flick Thor.
Jake Gyllenhaal also goes to great lengths when it comes to making movies, and doesn't mind undergoing a real-life transformation.
For the 2014 action thriller Nightcrawler, he lost over 30lb. Not because he had to, but because he felt it would suit the character better.
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Another actor who's no stranger to extreme weight shifts is Christian Bale. To play the part of chronic insomniac Trevor Reznik in the 2004 movie The Machinist, he famously lost over 60lb. Six years later he slimmed down to an extreme level again for The Fighter. But it was worth it as he won an Oscar for Best Supporting Actor for his role.
In 2013, he went to the other extreme and, after a diet of donuts and cheeseburgers, he appeared about 40lb heavier than usual for American Hustle.
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Charlize Theron also knows a thing or two about donut diets, who gained over 30lbs to transform from a beautiful model to play Aileen Wuornos in Monster.
Actress Renee Zellweger also famously gained weight to play everyone's favourite lovelorn diarist Bridget Jones, when she ditched her training regime and swapped salads for 4000 calorie meals.
Matthew McConnaughey is another actor who's shown extreme dedication to making movies. He shed 40b for his portrayal of Ron Woodroof in Dallas Buyers Club. He then went on to win his first Academy Award for the role in 2014.