Christian Bale, ‘American Hustle’ 

To more effectively play the role of New York con man Irving Rosenfeld, Christian Bale felt the need to gain a decent amount of weight. How much weight exactly? Around 42 pounds. 

Asim Bharwani via Wikipedia/CC BY 2.0 | IMDb

But other than just the weight, Christian Bale thought it necessary to also shave a part of his head. In total, the tactics earned him a physique far different than that he held for the Batman movies. We might say we prefer his Batman bod …

Anne Hathaway, ‘Les Misérables’

Anne Hathaway has a few things that some might say define her look. One of these would be her beautiful brown hair. But when she took on the role of Fantine in Les Misérables, she decided to chop it all off. 

Anthony Citrano via Flickr | IMDb

The haircut, in conjunction with a diet that excised most things tasty, left her looking wildly different for her role. The purpose was to “look like death,” she had said. Some might say it worked. Fortunately, it wasn’t hard for her to get back to health after filming. 

Emile Hirsch, ‘Into The Wild’

The movie Into The Wild — based, of course, on the best-selling book — featured Emile Hirsch at his finest. Not only did he portray the man, Chris McCandless, with elegance and ease, but he made an enormous transformation. 

Luke Ford via Wikimedia Commons/CC 2.5 | IMDb

To land the role, he dropped from his normal 156 pounds to the lower 130 pounds. But then, to shoot a scene in which he had become mortally ill in Alaska, he lost an additional 15 pounds. The dramatic transformation is one of the most mind-boggling in Hollywood. 

Jake Gyllenhaal, ‘Nightcrawler’

In the movie Nightcrawler, Jake Gyllenhaal stars as the psychopathic and sadistic stringer Lou Bloom. The character has a moral compass that has gone astray, which, interestingly, leads him to a thriving career as a paparazzo. 

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But to succeed in this role, Gyllenhaal wanted to lose a lot of weight — which is exactly what he did. For the role, Gyllenhaal cut down 30 pounds by running 15 miles a day and cutting most foods from his diet. A major transformation indeed. 

Renée Zellweger, ‘Bridget Jones: The Edge of Reason’

We all know Renée Zellweger from her roles in Bridget Jones’s Diary and Jerry Maguire. With these films, she won her way into our hearts with her delightful acting and pleasant demeanor. But she also won our amazement with one of her brilliant actor transformations. 

David Shankbone via Flickr | IMDb

For her role in Bridget Jones: The Edge of Reason, Zellweger gained a lot of weight to reprise her character. In total, she gained around 30 pounds. That’s a lot. A very impressive transformation, indeed. The actress later went on to snag her second Oscar for her performance in Judy.

Ryan Gosling, ‘The Lovely Bones’

While Ryan Gosling was not one of the leading protagonists in the film The Lovely Bones, he was originally intended to be. Unfortunately for him, his amazing transformation was not actually wanted by the director. 

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For the film, Gosling showed up to set having gained 60 pounds. Regrettably, the directors really had not wanted such a transformation. Because of this, the typically studly actor was replaced at the last minute by Mark Wahlberg. 

Colin Farrell, ‘The Lobster’

In The Lobster, Colin Farrell plays a man whose wife has recently left him. He is taken to a hotel where single people are meant to find a partner. To play this character, however, Farrell had to make a few substantial changes. 

FlynetPictures via Zimbio | IMDb

Farrell’s amazing transformation, as many might have predicted, revolved around weight gain. To fit into the role, he gained something around 40 pounds. The weight shows, and his commitment is admirable. 

Matt Damon, ‘Courage Under Fire’

In Courage Under Fire, Matt Damon plays an Army medic who retells the story of heroism on the part of Captain Karen Walden. But to play this troubled character, Damon had to make some huge changes. 

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Damon, however, instead of gaining weight, lost it — and lots of it. To fit into the role, he lost something around 60 pounds. Considering that the man is normally around 190, this was quite the transformation. 

Matt Damon, ‘The Informant!’

Matt Damon is known for many of his wild transformations in the movie world. For Courage Under Fire, for instance, he lost a whole lot of weight. But for The Informant!, Damon did the opposite. 

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For the movie, Damon felt it appropriate to gain around 25 to 30 pounds. Now, to be clear, this wasn’t muscle weight; it was doughy weight. While not as extreme as the weight he had lost previously, it is still a transformation worth mentioning. 

Ewan McGregor, ‘Fargo’

Ewan McGregor is known for many of his roles: Trainspotting, the Star Wars prequels, and The Island — all of these are movies in which he’s grabbed our attention. But in the TV series Fargo, he grabs our attention for just how different he looks. 

nicolas genin via Wikimedia Commons/CC BY-SA 2.0 | IMDb

For Fargo, McGregor shaved much of his hair back, gained some weight, and, ultimately, made a substantial transformation that blows our minds. While challenging, the transformation was one for the record books. 

Chris Hemsworth, ‘Thor’

Chris Hemsworth is another of those actors that we all know as a hunk. He’s large, in charge, and has played so many leading hunky characters that it’s hard to imagine anything less. But what does his past have to say about this? 

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This Hemsworth was not always as large and hunky as he currently is. Previously, he had the body of a surfer — not necessarily large. With Thor, however, he gained 20 pounds of muscle. Impressive.  

Christian Bale, ‘The Machinist’

Christian Bale might best be known for his role in the Christopher Nolan-directed Batman series. While he has had many major acting roles, this series was one of the most commercial. But for one of his lesser-known films, The Machinist, he made a major transformation that’s far different than his Batman physique. 

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In The Machinist, Christian Bale played a character that developed severe insomnia. Because of this, he began to deteriorate, losing health and all else. In total, he lost 63 pounds. This major transformation was due to a majorly restrictive diet. Fortunately, he’s back to good health now. 

Chris Pratt, ‘Guardians of the Galaxy’

In the show that is likely the greatest impetus to Chris Pratt’s fame, Parks and Recreation, the man played a lovable yet mildly portly character by the name of Andy Dwyer. For his later role in Guardians of the Galaxy, however, this physique drastically changed. 

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For Guardians of the Galaxy, Chris Pratt gained much muscle mass — and lost lots and lots of weight. In total, he lost around 60 pounds. This major transformation is something that would stick. 

Jake Gyllenhaal, ‘Southpaw’

When people train to portray boxers or professional fighters in movies, they typically get fairly large. For Jake Gyllenhaal, this was no different. 

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In total, Gyllenhaal gained around 15 pounds of muscle to play a fighting role in Southpaw. To prep to be the protagonist, he worked out around six hours a day for six months. The transformation is huge, and all you have to do is see his body to agree. 

Jonah Hill, ‘Maniac’

Jonah Hill perhaps earned the most fame from his role in Superbad. In that film, he nearly typecast himself as the corpulent funny character. However, it became clear that the man was versatile when he began to shift weight for roles. 

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For his role in the movie War Dogs, this became especially salient. He was required to gain weight — a lot of weight. In total, he gained around 40 pounds. In the more recent Netflix series Maniac, however, he lost all this weight and more. This led him to a commendable transformation. 

Matthew McConaughey, ‘Dallas Buyers Club’

Dallas Buyers Club is a movie for which many actors underwent stupendous transformations. Of these, Matthew McConaughey’s might have been one of the most amazing. 

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While we know him as a thorough stud, for this role he lost much of his body weight. Playing the famous AIDS victim Ron Woodroof, McConaughey fit the role by cutting 40 pounds. You can see the transformation for yourself. 

Natalie Portman, ‘Black Swan’

Natalie Portman is renowned as one of the most beautiful and talented actresses around. She’s also starred in too many movies to count. For one of these movies, however, she made a surprising transformation. 

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For her role in the movie Black Swan, she lost a dramatic amount of weight. What she did was cut 20 pounds, as she was shooting for an emaciated-looking figure. Her tactic worked, which made her part that much more impressive. 

Jared Leto, ‘Dallas Buyers Club’

Jared Leto is another of those actors that dedicated a lot of time to transforming his body in preparation for the movie Dallas Buyers Club. And, like McConaughey before him, this transformation involved losing a lot of weight. 

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Leto, unlike McConaughey, played a cross-dresser of sorts that had a bit of a substance problem. And with these character traits, he felt the need to undergo an impressive weight loss transformation. 

Naomi Grossman, ‘American Horror Story’

Naomi Grossman had to undergo quite the transformation with the makeup team on the set of ‘American Horror Story’. This particular character takes three hours in the chair to complete, including the buck teeth, shaved head, and prosthetic ears.

IMDb via FX

She recalled how people would say they could never sit in makeup for that long in an interview with Us Weekly. To which she consistently responds, “Really, you couldn’t go to your job, and lay back and close your eyes for three hours?”.

Tom Hardy, ‘Bronson’ 

Charles Bronson was one of the most notorious criminals in the British justice system. After having been arrested for petty crime, his sentencing quickly went up for extremely bad behavior. 

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To play Bronson in a recent biopic, Tom Hardy underwent a transformation that didn’t involve losing weight, but one that involved gaining a whole lot of muscle. The man got huge, and this was an amazing transformation indeed. 

Jared Leto, ‘Chapter 27’

In the movie Chapter 27, Jared Leto plays the assassin who killed John Lennon. To represent the man’s hefty frame, he had to gain some weight — and not just a little weight, a lot of weight. 

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To play the character, Leto gained a total of around 67 pounds. That’s roughly a third of his body weight. The transformation was so huge that Leto then struggled to walk to the set. Either way, his transformation was both impressive and formidable. 

Charlize Theron, ‘Monster’

Many people balked when they saw what happened with Charlize Theron in the movie Monster. Not only did she put on weight, she shaved parts of her eyebrows. The transformation was so mind-boggling that many neglect to realize it’s even the same person. 

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In total, Theron put on around 20 pounds for her role as Aileen Wuornos, the notorious serial killer. Her transformation is in part what earned her a sterling reputation as an actor (as well as an Oscar for Best Actress!). 

Demi Moore, ‘G.I. Jane’

To play the role of G.I. Jane, known formerly as Lieutenant Jordan O’Neill, Demi Moore had to make some substantial transformations. For the most part, this entailed changes to her diet and exercise routine. 

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To have time to film, Moore would start her exercise at 4:00 a.m. She also trained with a veteran Navy SEAL. Ultimately, her training made her the G.I. Jane she needed to be. 

J.K. Simmons, ‘Justice League’ 

Most of us know J.K. Simmons from his role in Spider-Man and other films. In one of his more recent films, however, he had to make some changes that would radically transform his body. 

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This film was Justice League. Here, Simmons had to put on lots and lots of muscle weight. In total, his transformation put his body in the best shape it has ever experienced. And it shows. 

Chris Hemsworth, ‘In the Heart of the Sea’

Again, Chris Hemsworth is one of those actors that we know as the stereotypical hunk. However, when he took on the role of Owen Chase, the stranded-at-sea sailor of the 19th century, that would all have to change. 

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To play this role, the already slimmed-down Hemsworth lost another 15 pounds. Considering the weight he lost for the role he played immediately prior, this led to a radical transformation. 

Tom Hanks, ‘Cast Away’

In Cast Away, Tom Hanks plays a man stranded ashore a tiny island. To fit the role, he engaged in a very specific diet similar to what he might eat were he an actual castaway. 

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In total, the paucity of calories induced Hanks to lose around 50 pounds. He nailed the transformation, acquiring the look of an emaciated castaway in no fewer than four months. 

Edward Norton, ‘American History X’

To play the radically minded and unsavory character Derek Vinyard, Edward Norton had to undergo quite the transformation. This transformation involved rapid weight gain in the form of muscle. 

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To play the role, Norton worked out relentlessly, gaining something around 30 pounds of muscle. The result was a large man who you wouldn’t want to mess with. 

50 Cent, ‘All Things Fall Apart’

In the movie All Things Fall Apart, the rapper 50 Cent plays a football player recently diagnosed with cancer. The athlete went from healthy to emaciated in a matter of months. 

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The change was implemented in 50 Cent with a liquid diet and incessant time on the treadmill. Ultimately, the actions lost him something like 60 pounds. The new weight of 160 pounds left him looking thin and insalubrious. Great transformation. 

Ryan Reynolds, ‘Blade: Trinity’

Ryan Reynolds wasn’t always the jacked hunk that many of us see him as today. In fact, he used to be a skinny man who engaged in nothing but juvenile antics on the screen. For the movie Blade: Trinity, however, he made some major changes. 

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To play this role, Reynolds put on something like 25 pounds of muscle. Ever since then, Reynolds’ career has soared. The major transformation here is something that Reynolds wanted to stick.

Taylor Lautner, ‘The Twilight Saga: New Moon’

Most of us know Taylor Lautner as the hunk from Twilight. He plays a werewolf with a crush on our protagonist, Bella. The man is clearly very active and seems to have always been that way. But has he? 

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Lautner was not always in such great shape. Before this role, he was something we might call a twig. But between the first and second Twilight films, Lautner gained 30 pounds of muscle. Quite the formidable transformation. 

Will Smith, ‘Ali’

The lovable actor from The Fresh Prince of Bel-Air was not always the man we know today as Will Smith. When he was younger, he didn’t exactly have much weight. But, to get ready for the role of Muhammad Ali, he had to change this. 

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To pull this off, he underwent a transformation from which he would not return. This transformation was one in which he gained a whole lot of weight — muscle weight. In total, he gained 35 pounds of muscle. Wow. 

Ethan Suplee, ‘The Hunt’

Ethan Suplee was always known for being the larger man on set, often the comedic relief too. However, he recently showed the world that he didn’t have to be an overweight character.

Instagram via @ethansuplee

This transformation shows Suplee after a lot of time spent in the gym. He’s looking better than ever and we’re surely going to see him take on more prominent roles now that his image is cleaned up.

Tom Cruise, ‘Tropic Thunder’

Tom Cruise isn’t normally one of those actors who tosses his physical health to satiate the requirements of a role. Rather, he chooses roles that typically cater to the physique he already has.

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And so, when we saw his cameo in Tropic Thunder, playing the lucrative and powerful producer Les Grosman, we were dumbfounded. This transformation is one that’s tough to forget (some might say it’s tough to unsee).

Mathew McConaughey, ‘Gold’

We’ve seen some of Matthew McConaughey’s amazing transformations already. For the most part, however, these have revolved around gaining muscle mass or loosing lots of weight. It wasn’t until the movie Gold where we would see this change.

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For the role, McConaughey put on a staggering 47 pounds. But beyond that, he shaved much of his beautiful locks. Together, these culminated in quite the amazing transformation. Yikes is all we have to say.

Michael Fassbender, ‘Hunger’

Michael Fassbender has been known for his roles in Hollywood films that require a bit more brawn. He’s played, for instance, a leading antagonist in X-Men, a “Nazi-hunter” in Inglourious Basterds, and an Assassin in the videogame remake Assassin’s Creed.

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In the movie Hunger, however, Fassbender had to lose a lot of weight to replicate the experience the starvation. And, due to his exceptional job, we see a man who has undergone a severe and amazing actor transformation.

Sylvester Stallone, ‘Cop Land’

Sylvester Stallone is one of those characters most of us only know as a brawny and heavy man. Having starred in some of the most successful franchises as such a character this makes sense. Rocky and Rambo are well-known and career-defining.

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In Cop Land, however, Stallone sought to change this. And, rather than lose a lot of weight, Stallone gained it — and it shows. In the role, you can see Stallone a bit more chunky, gut and all. We definitely prefer the old Stallone.

Johnny Depp, ‘Black Mass’

Johnny Depp is one of those characters that we don’t necessarily know as beefy and brawn. This doesn’t, however, mean that he often hasn’t been thought of as a sort of “sex” symbol. Much of this would change with the movie Black Mass.

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In the film, Deep had to transform to become the mob leader Whitney Bulger. For this transformation, Depp had to shave his head, gain a whole lot of weight, and get a bit overly aggressive. The transformation is, needless to say, amazing.