Actors are frequently called upon to change their appearance for movies, but sometimes they go well beyond the call of duty. This is a list of the 15 most amazing celebrity transformations for film.

15. Renee Zellweger Bridget Jones

For her part in Bridget Jones’ Diary, Renee gains nearly 13 kilos (28 pounds). She is one of the few on the list who probably look better after the transformation than at her normal weight.

14. Charlize Theron Monster

Granted, it is makeup - but not only is this incredible transformation a physical one, it is also an incredible transformation of attitude. It is hard to believe that the woman in the first photograph is the same beautiful, graceful woman in the second.

13. Hilary Swank Boys don’t Cry

In Boys Don’t Cry, Hilary Swank plays a girl who wants to be a boy. Her gender transformation ultimately leads to problems. This film is based on a true story.

12. Ellen Burstyn Requiem for a Dream

Ellyn Burstyn, most famous for her role as the mother in The Exorcist, appears in Requiem for a Dream as a prescription drug addicted woman who takes speed for weightloss.

11. Benicio Del Toro Fear and Loathing in Las Vegas

Normally a suave, slim man in movies, here we see Benecio after a very large weight gain for his role in Fear and Loathing in Las Vegas.

10. Jared Leto Chapter 27

Jared Leto gained a huge amount of weight (making him virtually unrecognizable) in order to play the part of Mark Chapman - the assassin of John Lennon.

9. Gary Oldman The Contender

Gary Oldman is a very versatile actor with a great reputation for being able to adapt to varied roles. Another great transformation by this same actor is, of course, when he played the character of Drexel in True Romance.

8. Donnie Wahlberg The Sixth Sense

Here we see the normally buff actor Donnie Wahlberg (brother of Mark Wahlberg - AKA Marky Mark) slimming down to play a psychotic patient of the character played by Bruce Willis in the Sixth Sense.

7. Edward Norton American History X

With American History X, Edward Norton really changed the way people looked at him. For this film he bulked up and plays a hard-nosed white supremacist.

6. Tom Hanks Castaway

Hanks lost an immense amount of weight for his role in Castaway. When he starts out in the film he is his normal weight - over the duration of filming he slowly slims down to almost dangerous levels.

5. Robert De Niro The Untouchables

Here we see an unusually large Robert De Niro playing the part of Al Capone in this Brian de Palma film.

4. Vincent D’Onofrio Full Metal Jacket

D’Onofrio gains an immense amount of weight to play the part of the somewhat simple Private Pyle in this brilliant Kubrick film.

3. Eric Bana Chopper

Here Bana gains weight and loses muscle mass to play the part of Mark Read. This film tells the intense story of Mark “Chopper” Read, a legendary criminal who wrote his autobiography while serving a jail sentence in prison.

2. Gerard Butler 300

Gerard Butler bulked himself up for his role in 300 as King Leonidas. The result of his efforts is the envy of virtually every geek in the world!

1. Christian Bale The Machinist

For this role of insomniac Trevor Reznik, Christian Bale lost 28.5 KG (63 pounds) for his role in this film. In order to lose weight, he ate one apple and one can of tuna per day. This is the largest amount of weight any actor has lost for a film. It was a hard decision for first and second place on this list - but Bale came first because he has managed to gain and lose weight rapidly for various roles - all within a short timeframe.

Bonus One: Gwyneth Paltrow Shallow Hal

Gwyneth Paltrow did an amazing job gaining so much weight for Shallow Hal - and then losing it all again afterwards! You will notice above that she barely fits in the first photograph, whereas a mere year later, there is plenty of room for her. Her dietician must be making a fortune!

Bonus Two: Elijah Wood Lord of the Rings

The dimensions of the images above don’t truly show the great transformation that Elijah Wood underwent for his role in the Lord of the Rings. Not only did he manage to grow hair on his feet and enlarge them, he managed to knock a few feet off his height. I can’t even begin to imagine the surgeries he must have undergone to reduce his height so much - or, in fact, the reversal operation which made his legs the right length again. What an amazingly dedicated actor.