1. Chris Hemsworth, Thor
Although Chris Hemsworth was already in fantastic shape before he took on the role of Thor, he wasn't bulky enough to be considered a Norse God. Few actors have been as excited to pack on mass like Hemsworth, but he did it with a positive attitude, and the results paid off.
Hemsworth hit the gym with former Navy SEAL Duffy Gaver, who used bodybuilding techniques to turn this once-skinny actor into an absolute beast. They focused on Hemsworth's arms and shoulders because Thor is sleeveless most of the time. He gained about 20 pounds, and he has maintained that physique ever since. His wife is one lucky lady.
2. Christian Bale, The Machinist
Compared to Chris Hemsworth, Christian Bale had to drop some serious weight for his role in The Machinist. His character is extremely thin due to insomnia, so Bale went from 173 lbs to 110 pounds, and he took drastic measures to lose those 63 pounds.
To drop the weight in four months, Bale only ate one can of tuna and an apple each day with black coffee and water for drinks. He only ate around 260 calories per day, and he was exercising on top of that. We don't know how he survived like this, and he must have been excited to eat normally again once the movie was finished.
3. Chris Pratt, Guardians Of The Galaxy
If you are a Parks and Rec fan, you will remember the days when Chris Pratt played the adorably chubby Andy Dwyer. Pratt didn't start focusing on his physique until he landed the lead role in Guardians of the Galaxy. Six months after being given the role of a lifetime, Pratt dropped 60 pounds.
Pratt described his regimen as "three or four hours a day of consistent a**-kicking hard work." Like Chris Hemsworth, he also worked out with Duffy Gaver, and Marvel assigned Phil Goglia as his nutritionist. He drank a lot of water and ate a lot more protein to compensate for how much he was working out.
4. Jake Gyllenhaal, Southpaw
When Jake Gyllenhaal played a middleweight boxer in Southpaw, he needed to be in the best shape of his life. To prepare for the role, he worked out six hours a day for six months and trained at the same gym as Floyd Mayweather.
Gyllenhaal was so committed to the role that his relationship with Alyssa Miller ended. He was putting so much time into perfecting his body, and he was able to walk away proud of the results. Everyone who worked with him was impressed by the amount of determination he had. This wasn't the only role he transformed for, though.
5. Jonah Hill, Maniac
Throughout the past decade, Jonah Hill's weight has fluctuated greatly for his different roles. In 2014, he slimmed down for his role in 22 Jump Street; however, he had to gain 40 pounds just two years later for War Dogs.
Today, Hill maintains a much slimmer figure, and he is almost unrecognizable from some of his burlier roles. If you look at him in movies like Superbad, The Sitter, or This is the End, he looks like a different person than compared to the actor we know today.
6. Matthew McConaughey, Dallas Buyers Club
One of Matthew McConaughey's most astounding roles was in Dallas Buyers Club. He was so dedicated to the role that he lost 40 pounds to prepare for the based-on-true-events story of AIDS patient Ron Woodroof. People were concerned for his health and ability to complete the 25-day shoot, but he assured everyone he was full of energy.
Although he lacked energy in his body, McConaughey said he was mentally sharp. He met with a nutritionist and gave himself four months to lose the weight. He did it in the healthiest way possible and wanted to make sure he made his physique as realistic as possible.
7. Natalie Portman, Black Swan
Although Natalie Portman had a dancing body double in Black Swan, she still had to go through intense ballerina training that made her think she would die. She lost 20 pounds for the role with a questionable diet and eight hours of rehearsal a day.
Portmans said she ate carrots and almonds for her strict diet, and the film left her physically drained. During rehearsals, she dislocated a rib, which made her understand the grueling life of a professional ballerina. However, many professional ballerinas have commented that the film's portrayal of their career was a bit exaggerated. It sure made for great cinema though!
8. Jared Leto, Dallas Buyers Club
Like his costar Matthew McConaughey, Jared Leto also had to prepare for his Dallas Buyers Club role physically. He was already a slim guy, but Leto still lost a whopping 40 pounds to play the transgender woman who suffers from AIDS. To get to his goal weight, he took extreme measures.
Leto said he stopped eating, which is not easy, and it is dangerous for your health. After losing all that weight, he said it changed him and how he would do things in his daily life. Leto is extremely dedicated to his craft, and this wasn't the only role he had to drastically change his body for.
9. Tom Hardy, Bronson
Tom Hardy looks almost unrecognizable in Bronson. He only had five weeks to turn himself into Britain's most dangerous criminal, and he put on seven pounds a week without steroids. He did whatever he could to bulk up but, luckily for him, his diet wasn't strict because they weren't going for a cut look.
Hardy mainly focused on his arms and shoulders, so his legs looked funny compared to his top half. The real Charles Bronson was disappointed when he saw Hardy because he thought it wouldn't work; however, two weeks later, Hardy came back and proved himself physically and professionally.
10. Jared Leto, Chapter 27
Leto always goes to the extreme when he has to change for a role physically. In Chapter 27, Leto plays John Lennon's assassin, Mark David Chapman, and he had to gain 67 pounds to resemble him. However, it wasn't a walk in the park to gain so much weight, and it took a physical toll on Leto.
By the end of filming, Leto could no longer walk to set, and he developed gout. Although it caused physical problems, Leto said it was the best way to slip into Chapman's skin because he felt miserable, and it helped him understand the character better.
11. Charlize Theron, Monster
Charlize Theron is not just another pretty face in Monster. While preparing for the role, Theron gained 30 pounds to portray Aileen Wuornos, the real-life serial killer. This role was a turning point in her career because people started to understand just how talented she was.
To gain weight, Theron ate donuts and potato chips to look more like Wuornos. She said it wasn't about getting fat; it was more about letting herself go to feel more like Wuornos. Theron has also had to drop a lot of weight for roles, and we don't know which is more challenging.
12. Demi Moore, G.I. Jane
Turning yourself into a Navy SEAL Lieutenant isn't an easy task, and Demi Moore went through intense training to prepare for that role in G.I. Jane. Moore would start training at four in the morning with a real Navy SEAL, with a routine that included running, strength training, and martial arts.
Moore pushed herself to the extreme and fully immersed herself in the role. She shaved her head, did actual Navy SEAL obstacle courses, and underwater running. She exuded girl power, and it was such an essential role for women everywhere.
13. J.K. Simmons, Justice League
Just when you thought J.K. Simmons was getting old, he comes back with his ripped body and proves that age is just a number. For the 2017 film, Justice League, Simmons portrayed Commissioner Gordon, and he was fully dedicated to his gym regimen.
Simmons worked with ex-Marine Aaron Williamson, who provides elite-level training to some of Hollywood's buffest stars. After the film wrapped, Simmons kept up with his routine because he never wanted to worry about health problems again. By now he can probably outlift most of us.
14. Chris Hemsworth, In The Heart Of The Sea
Chris Hemsworth might've bulked up to play Thor, but he had to drastically drop weight to star in the film based on real events, The Heart of the Sea. Hemsworth had already lost weight for a previous role, so it was challenging to lose the extra 15 pounds for this film.
He played a seaman whose ship is destroyed by a whale, and the crew has to survive on lifeboats. They had to continue to lose weight throughout filming to depict starving men. He said he and his castmates only talked about who looked the skinniest and who was able to lose the most weight.
15. Tom Hanks, Castaway
In one of Tom Hanks' most famous roles, he went through two different transformations. At the beginning of the movie, Hanks had to put on 50 pounds to depict a middle-aged man. However, after those parts of the film were shot, he took a year off to transform for the rest of the film.
Within four months, Hanks dropped 55 pounds on a strict diet and exercise regimen. His diet consisted mostly of seafood, vegetables, and a little fruit. When he got hungry, he would eat large amounts of vegetables. The diet later became known as "The Castaway Diet."
16. Edward Norton, American History X
Before American History X, Edward Norton wasn't a highly regarded actor. He had a few flicks under his belt, but nobody could have predicted just how memorable his performance of raging neo-Nazi skinhead Derek Vinyard would be.
Norton looked like he had been lifting weights for years, so how did he go from scrawny to brawny? He had a high-protein diet and did a lot of strength-building exercises like squats and presses. Norton gained 30 pounds of muscle to look like a street-tough gang leader.
17. 50 Cent, All Things Fall Apart
50 Cent is typically known for his buff body and catchy songs, but he became unrecognizable for his role in Things Fall Apart. The rapper played a football player diagnosed with cancer, and he shed 60 pounds for the role.
For nine weeks, 50 Cent was on a liquid diet and spent three hours a day on the treadmill. He usually weighs around 214 pounds, but he went down to 160. He said he felt like he was starving, and he had his arm tattoos removed to cut down on the time spent in makeup.
18. Matthew McConaughey, Gold
McConaughey famously lost 38 pounds for Dallas Buyers Club, but this was a role that required him to do the opposite. The typically athletic actor put on 47 pounds to play Kenny Wells in Gold. It was the first time he gained weight for a role without adding muscle, which must've been a nice break allowing him to finally drink and eat whatever he wanted for six months.
McConaughey had a much easier time packing on the pounds because he ate a lot of cheeseburgers and drank beer. He also stopped working out and wouldn't even climb stairs because that was too much exercise. His kids loved it because he said yes to whatever food they wanted.
19. Zac Efron, Baywatch
Although Zac Efron has always been in good shape, he had to build a lot of muscle to prepare for Baywatch. He went from looking like a teenage boy to the kind of man who turns heads wherever he goes during the period, but it wasn't an easy task. Efron worked out four to five times a week for six months and ate a clean and lean diet.
Efron worked with a trainer who pushed his functional limits to the max, with different workouts every day so he wouldn't hit a fitness plateau. Basically, to achieve this physique, you have to work out three times a day, switch up the workouts, eat a whole-foods diet, and listen to your body. Easy, right?
20. Robert De Niro, Raging Bull
Before Christian Bale and Matthew McConaughey stepped onto the scene, Robert De Niro was the king of transformations. In Raging Bull, De Niro plays an Italian boxer whose self-destructive behavior wears him down over a few decades.
De Niro gained 60 pounds, which was the most anyone had gained for a role at the time. However, it changed his physical appearance significantly, and it was only for the last few scenes of the film. Throughout most of it, he had to maintain a boxer's physique. To gain weight, he stopped production and went to Italy to eat as much pasta as he wanted. Now that's what we call dedication.
21. Vincent D'Onofrio, Full Metal Jacket
Vincent Donofiro's role in Full Metal Jacket changed his life and perception of the world forever. Before the role, he was athletic, rugged, and a man that had no problem attracting a woman's gaze. However, once he gained nearly 70 pounds, everything changed.
His physical transformation was shocking, and it took a toll on him physically. D'Onofrio said he could barely tie his shoes, and he was out of his element. It made him realize the typical things about beauty are much more profound than most people think.
22. Michael Fassbender, Hunger
To get into character for Hunger, Michael Fassbender had to become skin and bones, basically. The fit actor lost 42 pounds to become a prisoner who led the Provisional Irish Republic Army hunger strike in 1981.
To lose weight, Fassbender had a strict 900-calorie-a-day diet and did cardio workouts. He said it was like a psychological prison because he could only think about what he was eating and how to lose weight, and he took it to the extreme.
23. Ryan Reynolds, Blade: Trinity
Back in the day, Ryan Reynolds admits that he didn't live the healthiest life. He ate and drank whatever he wanted until he landed the lead role in Blade: Trinity. After three months involving six workouts a week and a strict diet, Reynolds put on 25 pounds of muscles.
This movie changed his career because Reynolds now looked like the muscly man people wanted to see. He has now acted alongside some of the most decorated names in Hollywood, and he has been offered superhero roles that require a fit physique.
24. Christian Bale, American Hustle
Christian Bale is all about method acting, so he goes all-in to transform for a role. For his role in American Hustle, Bale not only gained 42 pounds to play con-man Irving Rosenfeld, but he also shaved parts of his head to emphasize the character's combover.
On top of everything, Bale herniated a disk in his back because he gave the character a slouched posture. This reduced his real height by three inches. Even Robert De Niro was impressed by his transformation and couldn't recognize him right away.
25. Anne Hathaway, Les Miserables
Although Anne Hathaway was known for her gorgeous brown locks, she had to chop them off for her incredible role in Les Miserables. The talented actress also lost 25 pounds with a restricted diet which consisted of only eating two dried oatmeal squares a day!
Hathaway said it was the most consuming thing she had ever done because she had to look like she was near death. It was like a break from reality, and it took her a few weeks after filming to start feeling like herself again.
26. Daniel Radcliffe, Jungle
Although we are used to seeing Daniel Radcliffe battling Voldemort, he has since grown out of his Hogwarts days to play serious roles. In the movie Jungle, Radcliffe plays Israeli adventurer Yossi Ghinsberg who was lost alone in the Bolivian Amazon for three weeks. The character lost weight due to hunger, infection, and disease, so Radcliffe had to trim down.
Before the shoot, Radcliffe ate a chicken breast and a protein bar for two weeks before the shoot to look thin. He said it was a really unsafe way to lose weight, but it was worth it to have the huge meal after filming wrapped up. Radcliffe said it would have been weird to play the character and then go home and eat steak each night.
27. Ben Kingsley, Gandhi
When it came to playing Gandhi, Ben Kingsley wanted to be as authentic as possible. He shaved his head, lost 20 pounds, and followed Gandhi's vegetarian diet. Kingsley also studied yoga, started meditating, and learned to spin cotton thread on a wooden wheel as Gandhi did.
Kingsley fully immersed himself in Gandhi's lifestyle, and it helped him become the character inside and out. It paid off, and people respect him as an actor because of this role. It earned him an Acadamy Award for "Best Actor," as well as many other awards.
28. Emile Hirsch, Into The Wild
Emile Hirsch underwent a drastic transformation to play Chris McCandless, the man who ventured alone into the Alaskan Wilderness and sadly ended up starving to death. The actor lost 26 pounds for the start of the movie and then another 15 to show the change as his character starved.
Hirsch said it was a hard transformation because he has a sweet tooth and always craves candy. He dropped the weight by running and restricting his calories during the two stages of weight loss. It must have been nice to eat candy when he finished filming.
29. Jake Gyllenhaal, Nightcrawler
Did anyone else think Nightcrawler was the creepiest movie ever? To get into the character of Lou Bloom, a crazy paparazzi who stalks the dark streets of LA for shocking news, Jake Gyllenhaal wanted to look like a gaunt person who doesn't sleep.
Gyllenhaal kept a diet of kale, salad, and chewing gum while filming, and he also started running. Not only did it take a toll physically, but it also affected his personal life. He was shooting all night and barely ate, so he didn't see his friends and only noticed the effect of the movie in post-production.
30. Renee Zellweger, Bridget Jones: Edge Of Reason
After slimming down for her iconic role in Chicago, Renee Zellweger had to gain 30 pounds for the Bridget Jones movies. Although gaining weight might be easy for some of us, Zellweger had a more challenging time keeping her weight up.
Zellweger is naturally a tiny person, so she had to constantly eat to go from a size 4 to 14. After they finished filming, she went back to her regular eating and exercise habits, which caused her to drop all the weight. Everyone was concerned, but producers assured that the weight gain was just for the role.
31. Matthew Fox, Alex Cross
When Matthew Fox stepped onto the screen in Alex Cross, he looked nothing like his former self. The former Lost star said he wanted to radically change how he looked to be believable as the character, but he did it in a healthy way. Fox made sure he could still function for his family instead of going to extremes.
Fox wanted his physique to look natural, so he worked with a trainer and nutritionist to achieve the chiseled body people saw in the film. He trained hard, ate smart, and the results didn't have any unhealthy side effects because he did it properly.
32. Rooney Mara, The Girl With The Dragon Tattoo
Rooney Mara's transformation for Girl with the Dragon Tattoo made her look like a completely different person. She portrayed a pale, anorexic girl, and it took a lot of work to get to her desired look. She is already a slim girl, but she went on some kind of diet to lose weight.
Although she was tight-lipped about how she transformed, someone close to Mara said she was barely eating at the time. She also got plenty of piercings, dyed her hair black, and changed her haircut. It paid off in the long run because the movie made her a well-known figure in Hollywood.
33. Kit Harington, Pompeii
Unfortunately, when actors transform for roles, it can have lasting mental and physical effects. While Kit Harington was working out for the movie Pompeii, he developed body dysmorphia because he worked out so hard, and it became an obsession.
At his peak, Harington was working out three times a day for six days a week and suffered from exhaustion. Eventually, his trainer stepped in to make sure he was working out in a healthy way. In the end, he was happy with the results he achieved.
34. Emma Stone, Battle Of The Sexes
Although it might not look like much of a difference, Emma Stone had to train hard for her role in Battle of the Sexes. She wanted to do everything she could to accurately portray Billie Jean King and tell her story the right way.
Sled pushes, protein shakes, and a trainer named Jason Walsh were the keys to her success. Not only did she get into fantastic shape, but Stone also prevented injuries because she was physically prepared to play tennis all day. This strength gave her a new sense of confidence and self-love.
35. Ryan Gosling, The Lovely Bones
You might be scratching your head and looking up the cast of The Lovely Bones to make sure you didn't miss Ryan Gossling, but he wasn't actually in the movie. Initially, Gossling was cast as Jack Salmon, but the producers did not appreciate his 60-pound weight gain.
Gossling said he pictured Jack Salmon as this grieving father who turns to food and alcohol to cope, but the producers had other ideas. After being fired, Gossling said, "Then I was fat and unemployed," a sentence most of us would never imagine him saying.
36. Colin Farrell, The Lobster
Some actors get excited about their big transformations, and Colin Farrell was one of them. It wasn't hard for him to gain 40 pounds for his role in The Lobster because he had no portion control and could eat whatever he wanted.
Farrell was eating everything he normally ate, but he had double or triple the serving size. Once the movie wrapped, he was dedicated to getting back into shape, and again, it was also an easy transition. Not many people can say the same.
37. Taylor Lautner, Twilight: New Moon
Back when Twilight was still the biggest film sensation, our biggest problem was deciding between Team Edward or Team Jacob, but we only had that choice because of Taylor Lautner's transformation. Before the movie, he wasn't a scrawny boy, but he worked hard to gain 30 pounds of muscle in one year.
After Twilight, Taylor Lautner was a teen heartthrob, and his ripped body made every girl go crazy. He overcame his physical shortcomings and made a name for himself. It was a huge turning point in his acting career.
38. Hillary Swank, Million Dollar Baby
Hillary Swank's portrayal in Million Dollar Baby was something people might not have noticed, but her acting was incredible. To get into the body and mind of a female boxer, Swank had 90 days to learn how to box and get into the physical shape of someone who was always training.
Each day, Swank spent two hours boxing and two hours lifting weights six times a week. She gained 19 pounds of muscle even though the producers only asked her to gain ten. Swank ate 210 grams of protein per day, and even her sleep was coordinated into her daily routine. She had to wake up in the middle of the night to drink a protein shake because she couldn't go nine hours without eating.
39. Matt Damon, Courage Under Fire
Early on in his career, Matt Damon proved himself worthy of his Hollywood status. In the 1996 film Courage Under Fire, Damon lost 51 pounds by running 13 miles a day. However, that wasn't even the hard part for him; it was the diet.
Damon was only eating chicken breast, and he hated every second of it. He didn't have a chef or a nutritionist at the time, so he just made it up as he went along. Although it was difficult, it definitely paid off, and the results showed on the screen.
40. Will Smith, Ali
When Will Smith was rising to fame, he was a tall and slender guy. At 6'2," he was only 185 pounds, but for Ali, he packed on 35 pounds of muscle to resemble the heavyweight boxer, Mouhammad Ali. People were skeptical about him playing the boxer, but he proved them wrong.
Five days a week and six hours a day, Smith was in the gym for a year preparing for this role. He not only prepared physically, but he also got into the mindset of a fighter, so he adopted that lifestyle in every aspect. He slept, ate, and breathed fighting until the movie wrapped.
41. Matt Damon, The Informant!
In preparation for The Informant, Matt Damon thinks he gained around 30 pounds. He wasn't trying to get fat, but he wanted to appear doughy. Despite gaining weight for the role, he said his friends mocked him mercilessly, but it didn't bother him.
To gain the weight, Damon credits In-N-Out burgers and beer. He stopped working out and ate whatever he was craving, which was fun because he hadn't lived or ate like that since he was in his 20s. However, it was challenging to get the weight off once the movie was done.
42. Ewan McGregor, Fargo
When Ewan McGregor was cast in Fargo, the producers told him he had to put on weight. This was at a time when McGregor was in the best shape of his life after filming Trainspotter 2; however, he didn't protest eating dessert and everything else he wanted.
McGregor made sure he had carbs with every meal and added french fries to every order. It didn't take techniques or a dietician; he just did whatever he wanted. He also never weighed himself, but he had to buy larger pants.
43. George Clooney, Syriana
What's better than having a pasta-heavy diet to gain weight for a movie? We can't think of many things. When George Clooney starred in Syriana, he bulked up, shaved his hairline, and grew his facial hair. However, it wasn't all fun and pasta.
During a stunt, Clooney suffered a spinal injury because of the weight he gained for the role. He was bedridden for months, which is why he couldn't be in Ocean's Twelve. He eventually had to get surgery and said that ultimately, the weight gain was pretty stupid.