It's not about the talent people look for when an actor is widely acclaimed for their performance. It is the dedication that really inspires the actors and actresses to dig deep into their characters and project to us their stories as viewers.

Part of the role of an actor is to credibly turn into someone else and it often takes a little physical effort. These actors have completely transitioned from drastic weight loss or gain to being unrecognizable with believable prosthetics, lipstick, and wigs for their iconic parts. Let's take a look at some of the Top 25 incredible actor transformations for movie roles.

25. Ewan Mcgregor (Fargo)

Ewan Mcgregor in Fargo

Ewan Mcgregor was living the fittest life at the age of 45 when he was told that he had to put on some weight for his role in Fargo. “I ordered a massive dessert and started putting on weight from that second onward. I just started eating whatever I wanted. I made sure that I had carbs with everything and French fries with everything," he said in an interview for Vulture in 2017.

24. Kit Harington (Pompeii)

Kit Harington in Pompeii

An interesting fact that can be found on IMDb is that Kit Harington became so obsessed with working out for his role of Milo in Pompeii that went to the gym 'three times a day for six days a week'. His trainer had to intervene and make him stop.

23. Robert De Niro (Raging Bull)

Robert De Niro in Raging Bull

For his role of Italian-American middleweight boxer Jake LaMotta in Raging Bull, Robert De Niro had to undergo an incredible body transformation. De Niro played the younger boxer version of the character, and the older, overweight one. The actor had to go back to Italy and eat pasta to gain more weight, according to PK Baseline.

22. Rooney Mara (The Girl With The Dragon Tattoo)

Rooney Mara in The Girl With The Dragon Tattoo

In an interview for Vogue magazine, Rooney Mara admitted that she 'may been on a bit of a diet'. While having dinner in a restaurant, Mara ordered a piece of fish but she 'barely touched it'.

21. Edward Norton (American History X)

Edward Norton in American History X

For the role of Derek Vinyard in American History X, Norton had to take proteins and go to the gym in order to reach that 'raging neo-Nazi skinhead' look. As per Men's Fitness, Edward did exercises such as squats and presses.

20. J.K. Simmons (Justice League)

J.K. Simmons in Justice League

J.K. Simmons went full beast mode to get into shape for the role of Commissioner Gordon in Justice League, Men's Fitness suggest. He hired the personal trainer Aaron Williamson, who is a former marine and has worked with other Holywood stars such as Zac Efron, Dwayne Johnson, and Jamie Foxx.

19. Natalie Portman (Black Swan)

Natalie Portman in Black Swan

Natalie Portman endured a difficult change to play a ballerina in Black Swan. She lost 20 lbs, after having a very rigorous diet consisting of carrots and almonds, and spent eight hours a day in rehearsals. "There were some nights that I thought I literally was going to die," Portland admitted to The Independent.

18. Anne Hathaway (Les Miserables)

Anne Hathaway in Les Miserables

Anne Hathaway lost 25 lbs to star in Les Miserables. “I had to be obsessive about it—the idea was to look near death. It was definitely a break with reality, but I think that’s who Fantine is anyway,” she explained to HuffPost.

17. Ryan Reynolds (Blade: Trinity)

Ryan Reynolds in Blade Trinity

You wouldn't believe it but  Ryan Reynolds was your ordinary frat boy back in the day. “I was pretty unhealthy. I didn’t care what I ate or what I drank," he admitted to Men's Fitness. However, for the role of Hannibal King in Blade: Trinity, Reynolds worked out six days a week, and after three months, he gained 25 lbs of muscle.

16. Michael Fassbender (Hunger)

Michael Fassbender in Hunger

Michael Fassbender is known for losing an incredible 42 lbs for the movie Hunger. The actor had to go on a fasting of adding 900 calories each day and exercising such as yoga, skipping, walking, accoring to Men's Journal.

15. Tom Hanks (Castaway)

Tom Hanks in Castaway

Some have to lose and some have to put on weight for their roles. In the case of Tom Hanks for the award-winning Castaway, it's both. Hanks put on 50 lbs to picture a middle-aged man during the pre-production. However, when the production started, he lost 55 lbs and didn’t shave or cut his hair for weeks, WatchFit have claimed.

14. Zac Efron (Baywatch)

Zac Efron in Baywatch

Zac Efron was known for having a decent-looking muscle body, but when he appeared on TV as Matt Brody on Baywatch, everyone was positively surprised after noticing his shape. Zac had to stay away from sugar and carbs and follow a strict diet while enduring extreme workout sessions, as per E! News.

13. 50 Cent (All Things Fall Apart)

50 Cent in All Things Fall Apart

Back in 2011, American rapper 50 Cent appeared in the main role of All Things Fall Apart. He played Deon, a football player diagnosed with cancer and for the role, he had to lose around 60 lbs, NY Daily News once said.

12. Chris Hemsworth (In The Heart Of The Sea)

Chris Hemsworth in In The Heart Of The Sea

Chris Hemsworth lost 15 lbs while shooting In the Heart of the Sea. He played Owen Chase, a 19th-century seaman. “We all felt like a bunch of supermodels, trying to get down in weight for a show, or something," he told Entertainment Weekly.

11. Tom Hardy (Bronson)

Tom Hardy in Bronson

Tom Hardy played both Michael Gordon Peterson and Charles Bronson, but for those roles, he had no official regime. "I did very non-specific exercises such as press-ups, pushups, abs work, and resistance training. Also, to become Charlie Bronson I had to quickly put a lot of weight quickly on my forearms, chest, and neck," he said in an interview with AskMen.

10. Matthew McConaughey (Gold)

Matthew McConaughey in Gold

Matthew McConaughey is known for his athletic figure, but he had to change that for the role of Kenny Wells in Gold. He had to gain 47 lbs and revealed to E! News that he was allowed to war and drink whatever he wanted "Not that much sweets. Cheeseburgers and beer will do the trick,” he said.

9. Demi Moore (G.I. Jane)

Demi Moore in G.I. Jane

Playing the first female Navy SEAL in G.I. Jane required a change of lifestyle for Demi Moore. Pop Workouts have revealed that not only did she have to follow a diet and train to get into shape, but she also had to do martial arts, even be trained for a Navy SEAL mindset, and shave her head as well.

8. Matthew McConaughey (Dallas Buyers Club)

Matthew McConaughey in Dallas Buyers Club

We’ve mentioned Matthew McConaughey’s weight gain for his role in Gold, but for the role of Ron Woodroof in Dallas Buyers Club he had to lose a remarkable weight. His character is a rodeo cowboy diagnosed with AIDS who discovers a banned drug that can help patients survive longer. Eventually, he lost 40lbs for the shooting, according to Radio Times.

7. Jared Leto (Dallas Buyers Club)

Jared Leto in Dallas Buyers Club

Another famous actor who starred in the Dallas Buyers Club and had to overcome a great makeover is Jared Leto. In order to play Rayon, a transsexual with HIV and then AIDS, Leto got rid of 40 lbs. “I stopped eating, it wasn’t an easy thing to do,” he once told The Wrap.

6. Jonah Hill (Maniac & War Dogs)

Jonah Hill in Maniac (right) and in War Dogs (left)

Jonah Hill’s weight has oscillated throughout his career. He was mostly known to the public as having a full figure but eventually, he had to cut it down in 2014. Two years later, he added 40 lbs to play arms dealer Efraim Diveroli in War Dogs, as per Men's Journal. Then, in 2018, he surprised everyone with his lean figure in the TV miniseries Maniac.

5. Jared Leto (Chapter 27)

Jared Leto in Chapter 27

The extent Jared Leto went to for his most recent position could seem a tad intense. To plat the killer of John Lennon in Chapter 27, Mark David Chapman, Leto gained 67 lbs. As per the LA Times, his bodyweight reached the point when the actor could no longer walk to the set.4.

4. Matthew Fox (Alex Cross)

Matthew Fox in Alex Cross

Matthew Fox had to lose almost a fifth of his weight for the role of the villain in Alex Cross. We couldn’t put him on an extreme, low-calorie diet,” his trainer Simon Waterson told Men's Health. Fox trained very hard and stuck to his balanced diet.

3. Chris Pratt (Guardians Of The Galaxy)

Chris Pratt in Guardians Of The Galaxy

Imagine weighing 300 lbs and having the courage of auditioning for a Marvel movie? That’s what Chris Pratt did before losing 60 lbs in six months to land the role of Peter Quill/Star-Lord. His diet consisted of 4,000 calories per day and so much water. “I was peeing all day long, every day. That part was a nightmare,” Pratt told Men's Fitness.

2. Chris Hemsworth (Thor)

Chris Hemsworth in Thor

Chris Hemsworth took his job seriously when given the role of Thor, so much that he decided to become him. The actor started working out and teamed up with former Navy SEAL Duffy Gaver. They realized that Thor is rarely shown shirtless, but he usually appears sleeveless, Muscle and Fitness suggest. Thus, Hemsworth gained 20 lbs and added a large amount of arm muscle gain.

1. Christian Bale (The Machinist)

Christian Bale in The Machinist

One apple a day keeps the doctor away, right? Well, Christian Bale’s case, it landed him the role of Trevor Reznik, a machinist with severe insomnia, in The Machinist. Besides that, Bale was allowed to eat only one can of tuna fish as well – for four months! Thus, with only two types of foods a day and water and black coffee, he lost 63 lbs, Diethics say.