Sometimes a little make-up and a wig is not enough for actors and actresses to play the role they are required in a particular film. It is the extreme changes in their physical constitution that require great sacrifice and discipline to carry them out. We all know that actors and actresses have to prepare themselves in various fields before playing a role. But in this case, we will refer to their extreme physical transformations and body changes, which can often be life-threatening. People say that in order to get what we want in life, it is worth making great sacrifices, and these celebs are the perfect example. They have changed their bodies to play a role; and are the living proof of how important it is in Hollywood to not be typecast.

Extreme diets, hundreds of sweets and hamburgers, implants, aesthetic modifications, among other crazy things. Those are the reasons why these actors have received critical acclaim and recognition from the public, which has earned them the status of movie legends. Without a doubt, many of the following actors on this list have made a dramatic change in their appearance for their films, showing love for their work and for embodying their characters in the most credible way possible.

Christian Bale (The Machinist)

For the British actor there is never a middle ground. Bale often tests his physique in an impressive way; he is one of the actors who has most transformed himself on the big screen. In The Machinist, Bale acted as Trevor Reznik, an engine operator with severe insomnia. Lack of sleep leads to severe weight loss, so Reznik becomes extremely thin. To be suitable for the character, Bale went from 171 lbs. to 108. The actor followed a draconian diet: for almost four months he ate only one can of tuna and one apple a day, completing the "menu" with black coffee and water. To lose weight faster, the exercise regimen included intensive cardiovascular exercise. Christian Bale became a real skeleton, but not only is his physical change one of the most daring things any actor has ever done in history, but he also delivered a convincing characterization in a dramatic film worthy of applause.

Matthew McConaughey (Dallas Buyers Club)

In the movie Dallas Buyers Club, the remarkable weight loss of actor Matthew McConaughey is amazing. He lost more than 39 lbs. to make the story credible. In the movie he plays cowboy Ron Woodroof, a homophobe and drug addict who experiences the physical changes caused by AIDS. Woodroof was a businessman who challenged the U.S. government to bring unapproved drugs to other sick people, amassing good fortune. McConaughey explained how, despite others' concerns about the negative impact he might have on his health, he found he had a lot of energy, at least mentally, to complete the intense shooting. Matthew won the Oscar for Best Actor for his outstanding performance, not only is his skinny appearance convincing, but it was also the highest point in the Texan actor's career.

Charlize Theron (Monster)

The South African actress made one of the most dramatic changes in Monster, where she became a serial killer named Aileen Wuonos. In addition to changing her face through makeup, the sculptural figure of Charlize Theron was forgotten: she gained almost 22 lbs. Doughnuts, lots of fruit, and eggs were the diet in those days, so much so that it was almost impossible to know that it was the South African behind the character of Wuonos. Not only did Theron gain weight, but she also wore a prosthesis on his face and teeth, which meant long hours of make-up every day during filming. All this great work led her to win an Oscar for Best Actress, showing that for this lovely woman there is more than beauty inside her, but a lot of potential to play dramatic roles at the level of the greatest.

Chris Pratt (Guardians of the Galaxy)

Pratt waited until he was 34 to get in shape, just in time for the shooting of Guardians of the Galaxy. The Star-Lord character required some remarkable abs and the actor didn't hesitate to diet and exercise to get it. The miracle occurred after hard gym sessions (3-4 hours a day), running, swimming, boxing, the P90X fitness program and kickboxing. And along the way he dared to complete a triathlon. He was helped by a personal trainer and a nutritionist who imposed a diet of 4,000 calories a day, in addition to plenty of water: "I was peeing all day, that part was a nightmare," he told Men's Fitness magazine. "If you move your ass, it really only takes you six months to get like this. Six months go by quickly," he said in the Comic-Con.

Jake Gyllenhaal (Southpaw)

Gyllenhaal gained 15 lbs. of pure muscle to play the role of a medium-weight boxer in the film Southpaw. He worked six hours a day for six months at the Las Vegas gym of the undefeated boxing champion Floyd Mayweather Jr. The film's director, Antoine Fuqua, literally said they had turned Jake into a beast. "He's a very powerful fighter in this movie. He was very dedicated and gave his heart," Fuqua said. The actor spent so much time in the gym and was so committed to the role that his relationship with Alyssa Miller ended. The amount of time that must be devoted to it and the sacrifice made for this type of role is a great commitment, as well as a major acting challenge. Perhaps the film itself was not as surprising as Gyllenhaal's dedication, since it does not go beyond the traditional scheme of a fighter who redeems himself after a serious bump in his career.

Jared Leto (Dallas Buyers Club)

Jared Leto lost a surprising 39 lbs. to play the role of a transsexual with AIDS in Dallas Buyers Club, making him the second hero on the list for the movie. "I stopped eating, it wasn't an easy thing to do. I had to lose 30 to 40 pounds. After a while I stopped counting the pounds," said the musician and actor. To make the film, his weight dropped to 112 lbs., but not only that. The acting challenge was huge: it changed the way he walked, the way he sat... even, crazy as it may seem, the way he thought. The hard work, worthy of a method actor, and dedication rewarded him with several awards, especially the Oscar for Best Supporting Actor for his role in the film.

Natalie Portman (Black Swan)

Natalie Portman endured an intense schedule because of her role as a ballet dancer in Black Swan, which left her fearful that she almost fell seriously ill. The 29-year-old actress during that time lost 20 pounds to play her part. She only ate rations of carrots and almonds. Natalie, who won an Oscar for her performance of a desperately ambitious and perfectionist dancer, said, "There were some nights when I thought I was literally going to die." The film left her physically and emotionally exhausted, and it was surely the first time that Portman understood how she could immerse herself so much in a role that even her health could be in danger. However, the film received criticism from some professional dancers. Racheal Prince of the British Columbia Ballet said, "I'm sure every dancer struggles with little things here and there, but for a girl who struggles with all those problems, it makes us look crazy."

Tom Hardy (Bronson)

To become Charlie Bronson, British actor Tom Hardy had to gain weight quickly, gaining muscular mass especially in his forearms, chest and neck. By the time he finished, his legs looked like stork legs compared to the upper half of his body. "I had five weeks to become Britain's most dangerous criminal and it was a race against time. For Bronson, I set out to gain about three pounds a week, without steroids. In the end, I set a goal of 5 lbs., so I ate chicken and rice all day long. Then I also added pizza, ice cream from Häagen-Dazs and Coca-Cola: this was not a good idea, but I had to get fat. I needed to put a layer of fat on my body, because Bronson was a big guy when he was young, a fighter," Hardy said. Easily a diet that many of us may be eating right now, but not for a role.

Demi Moore (G.I. Jane)

Becoming Lieutenant Jane O'Neil, the first female naval officer, was not an easy task. Demi Moore's training to become Lieutenant Jane included real Navy exercises, combined with lots of cardio and martial arts. Her training began at 4:00 a.m., like a real military soldier, and by the time she finished her routine, she had time to take a bath and start shooting. Moore hired celebrity coach Gregory Joujon-Roche to get in shape, and Navy service instructor Stephen Helvenston to win that visceral Naval Service mentality. To immerse herself in the role, she shaved her head, did Navy obstacle courses and other military-style exercises such as running underwater, push-ups in the mud, just to name a few parts of her training.

Edward Norton (American History X)

Before he went public with American History X, Edward Norton was nothing more than an actor with a bad haircut and a few decent movies under his belt. Then he stepped on the screen as Derek Vinyard, a tough neo-Nazi skin-head with a physically imposing look that would make most men change sidewalks on the street. Norton not only had his biceps marked and his chest perfectly muscular, but he looked like a guy who had spent some time lifting weights in prison. His coach, Anthony Krotes, emphasized weight training with a lot of weight and few repetitions. The result was 28 lbs. of muscle, plus one of the best films not only in Norton's filmography, but also in the 1990s. American History X went onto become a critically acclaimed film.

50 Cent (All Things Fall Apart)

The famous Queens rapper, 50 Cent, lost almost 59 lbs. to play a football player who was diagnosed with cancer in Mario Van Peebles' movie, All Things Fall Apart. 50 Cent, named Curtis Jackson, normally weighs 213 lbs., ended up weighing 154 for this film. The rapper says he lost weight through a liquid diet and spending three hours a day on a treadmill for nine weeks. "I was starving," he said. 50 said that, to commit to the role, he also removed some of the tattoos from his arm to make this film, as he wanted to speed up the process in the make-up area to cover them up. Unfortunately, the artist's effort behind the album Get Rich or Die Tryin' (one of the most successful rap albums in history) was almost in vain, as the film was not well received by critics and viewers alike.

Zac Efron (Baywatch)

The actor worked with fitness trainer Patrick Murphy four to five times a week for six months to prepare for the big screen adaptation of the Baywatch series, while following a strict diet which did not sugar and carbohydrates for months. "I just thought it looked like lifting weights was hard enough," Efron said. "But instead of the typical bodybuilding moves I had become accustomed to, Patrick took me to my limits with a very multifaceted style: strength, explosiveness, rhythm, various cardio exercises and certainly quite exhausting." Without a doubt, Efron had fun, as he got to know first-hand the real effort of the greatest actors committed to a role. To avoid boredom or getting the muscles used to it, his trainer constantly changed the routine, which made each workout different and not so monotonous.

Vincent D’Onofrio (Full Metal Jacket)

Vincent D'Onofrio was a tall, graceful actor, 6 feet tall, with curly-dark hair. He wasn't a handsome man, but he didn't go unnoticed either. But after winning one of the main roles in the movie Full Metal Jacket, playing Leonard Lawrence, a fat, inept and increasingly frightening marine recruit, D'Onofrio was forced to gain 66 lbs. and shave his head. This was a physical transformation that had a shocking effect. The actor says that people used to tell him things twice because they thought he was stupid. His thighs were huge, his arms were fat and his nose was even fatter. Probably he had a hard time tying his shoelaces because of his weight, but I'm sure this was all part of convincingly characterizing Leonard Lawrence and making sure legend Stanley Kubrick was satisfied with his performance.

Robert De Niro (Raging Bull)

The physical changes of certain actors, due to the demand of the script, as you can see, have been around a long time ago. This is the case of Robert de Niro, who achieved a spectacular change of 59 lbs. for this film in 1980. For his role in Raging Bull, playing Jake LaMotta (an Italian-American middleweight boxer with a turbulent life), de Niro had to gain 59 lbs. to give real credibility to the physical decline of the legendary boxer throughout the film. In addition, the actor trained in such a hard way that he even fought in three real boxing fights in Brooklyn, winning two of three. As the shooting progressed, Robert de Niro had to make a dramatic change, going from showing off the remarkable musculature of a boxer, at the beginning of the film, to acquiring a voluptuous and obese figure at the end of the movie.

Christian Bale (Batman Begins)

Christian Bale's body has changed sharply on several occasions for his roles in the cinema. But without a doubt, its most drastic evolution was the move from The Machinist to Batman Begins. After weighing 108 lbs., only half a year later, he was playing Batman, reaching 198 lbs. of pure muscle fiber. Bale's training focused on increasing body mass combined with cardio (high intensity training), which made the actor look so different in just six months. And the results were clear: Bale convinced the whole world with his performance of Bruce Wayne/Batman, which was directed by Christopher Nolan. Eventually, they collaborated on two other films, The Dark Knight and The Dark Knight Rises. The story will recall not only the fabulous trilogy about The Dark Knight, but also the extreme body changes that Christian Bale had in order to play the bat.