Being a superhero is no easy business. They are constantly being shot at, they're dodging mystical and technological attacks from all sides, they save people (and the entire world!) on a daily basis, and they do all of that while looking remarkably good at it. For all of their heroic deeds, they have a heroic body to match. And yet, in a world where they live on the comic book page, you'll rarely see them rest, train or eat.

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But what about the actors that have to portray these powerful characters? Very real humans, with very real bodies to nourish. People with strengths who also have very real limits. As it turns out, being an actor can be no easy business either. To perfectly embody the roles they play, some actors have had to go through pretty insane body transformations. Here is a list of 15 actors who had (and still have) to shred their bodies to accurately portray characters with superhuman physiques.

15 HUGH JACKMAN

Hugh Jackman The Wolverine

When the first "X-Men" movie hit theaters, it was a different time for superhero roles. They didn't garner much in the way of attention and they didn't come with anywhere near as much anticipation. Fast forward to today, and the times have remarkably changed. However, none of that would have happened without Hugh Jackman's turn as the indestructible mutant with razor-sharp claws, a nasty temper and more veins on one's body than anyone could possibly count.

As the Wolverine, Jackman had to follow a very strict diet plan and spend countless hours in the gym. In doing that, he not only set the trend for what the audience expects out of a super-human body, he also continues to set the bar higher with every new iteration of his most famous role. At 48 years old, no one could ever fault him for announcing "Logan" as his final Wolverine movie. He's kept this up for more than 15 years, all while winning an all too real battle against skin cancer for the sixth time. At this point, one can only wonder if he is in fact, a real super-human. Congratulations, Hugh. We'll miss you in this role.

14 CHRIS PRATT

Chris Pratt as Star-Lord

In the early days of 2014, Chris Pratt was known to a smaller audience as soft, lovable goofball Andy Dwyer on the hit NBC comedy "Parks and Recreation." But all that changed with the release of "Guardians of the Galaxy." Suddenly, the man who had greeted Amy Poehler's Lesley Knope in the nude and ate marshmallow cream and toxic, silver-painted candy had become a sex symbol almost overnight thanks to his role as Peter Quill, aka Star-Lord.

In preparation for his role, Pratt reportedly lost around 60 pounds and shredded his body into that of a superhero by hitting the weights hard. His star-making turn as the leader of the Guardians launched him into the stratosphere of popularity and the man has become an inspiration for what people can accomplish if they just set their mind to it. Even more remarkable is that, three years later, he has kept the weight off, and the muscles on.

13 MELISSA BENOIST

Melissa Benoist As Supergirl

The hero known the world over as the one and only Superman casts a long shadow, one that most wouldn't dare crawl out of. But leave it to Melissa Benoist to rise up to the challenge. Sure, any being that hails from Krypton, under a yellow sun, can develop superhuman strength, heat vision and flight. But, man or woman, it takes a very real earthling to portray them. As "Supergirl," Benoist had a daunting task ahead of her: to make the audience believe that a woman can fly.

Being a hero isn't all about size. It's also about definition, strength, and stamina. Not everyone can pull off wearing that skin-tight outfit and cape and look as heroic as Benoist does. One can only imagine the long days of wire work and how strenuous that can be on anyone. With “Supergirl” entering its second season, Benoist has no choice but to keep working hard to keep wearing that S-shield, and has explained in past interviews that she's done so by focusing hard on a mix of core work, plyometrics, pilates and boxing.

12 GERARD BUTLER

Gerard Butler As King Leonidas

The movie "300" came barging into theaters with more adrenaline and fuel-pumping energy than anyone anticipated, and it left half the men in the audience feeling inadequate. Why? Mainly, because of its stars. All 300 of them. But none could compare to their leader, King Leonidas, portrayed by Gerard Butler. Wearing nothing but a glorified diaper, helmet and shield, Butler roared onto the screen with constantly flexed abs that made you wish you hadn't bought popcorn at the concession stand.

For his movie, director Zack Snyder brought in trainer Mark Twight to develop a workout that would turn his actors into Spartan warriors. While a quick Google search will give you a template of "The 300 Workout," it is but a taste of what Butler actually went through, with constantly changing sets and routines, and an insane, still-undisclosed diet plan. Secrets of the trade, it would seem. In fact, Butler and the casts' results were so remarkable that the relationship between Snyder and Twight wouldn't stop there.

11 GAL GADOT

Wonder Woman Gal Gadot

Amazonian. Goddess. Ambassador. Wonder Woman is all that, and more. She embodies strength and peace and beauty. She is a legend and a symbol. To find an actress to perfectly portray her was a challenge in itself, and yet in came Israeli actress and model Gal Gadot. Being a model, Gadot already knew what it was like to keep a fit body, but becoming Diana Prince would take a lot more than that. She would have to go on another level. And once again, "Batman v. Superman" director Zack Snyder called on his old friend Mark Twight.

With Twight's help and guidance, Gadot graced the screen with the presence and ferocity of the gods. In this case, the transformation was as much about developing strength in the body as in the mind. This is a Wonder Woman that isn't molded to look like a statue or a hulking beast. She is equal parts graceful, inspiring and deadly with a sword and lasso. Thanks to long hours spent in the gym working on her strength and endurance, Gadot was able to transform herself into someone viewers could believe is an actual goddess.

10 KATIE CASSIDY

Katie Cassidy Black Canary

Regardless of how you feel about the character on the CW's "Arrow," there is no denying the fact that Katie Cassidy gave her absolute all into this role. After being more or less sidelined for more than two seasons of the show, Cassidy was promoted full time to a leather outfit and a domino mask. Not one to shy away from the challenge, she took the responsibility of the role incredibly seriously, wishing to offer fans a Black Canary worthy of the title.

Kettlebells, circuit training, boxing; there is no exercise routine that would stop her. Laurel Lance's transformation from lawyer to masked vigilante was made all the more believable thanks to a devotion rarely seen from the leading actress of a weekly television series. One need look no further than the actress' own Instagram page to see just how much she can dish out in the gym. Equally dwarfing and inspiring, there is no denying that Cassidy gave the fans a Black Canary they deserved.

9 STEPHEN AMELL

Stephen Amell Arrow

"Arrow" came at a time when superheroes only belonged on the big screen, but thanks to a popularity due in no small part to its leading actor, the number of comic book-inspired television shows is now at an all time high. But before all that, there was just a shirtless man and his salmon ladder. It was a series of clinks heard around the world, even at a time when there was only a trailer for the show and nothing more.

Amell came to the role primed to take on the entire world. Ready to prove himself and set a new standard for what the audience could expect out of their weekly superheroes, he transformed his body into a veritable fighting machine. He learned to believably shoot a bow on screen, took parkour lessons and learned to fight, all of which is on top of his regular gym sessions. It's something he keeps doing to this day, now well into the fifth season of his show.

8 CHRIS EVANS

Captain America The First Avenger Chris Evans

Chris Evans was always an actor in good shape, but when he was cast as Captain America in "The First Avenger," he signed on to portray the world's first super-soldier and had to have a body to match that. While scrawny pre-serum Steve Rogers was a mix of C.G.I. and a body double, there is no denying the fact that when those transformation chamber doors opened in the movie, Evans appeared as a real superhero that made some gasp, and others, quietly sigh.

Gaining and sustaining 30 pounds of muscle is no easy feat, and yet Evans manages to achieve it in spades. Going from "The Avengers" to "The Winter Soldier," "Age of Ultron" and "Civil War," Evans has to keep putting in the work, and he keeps impressing every time. Thanks to his dedication, this is a role he has become synonymous with and he has no one to thank other than himself. After all, it's not every day that a single bicep flex can land a helicopter, and yet Evans made us believe it.

7 BEN AFFLECK

Ben Afleck Batman Training

Christian Bale would always be a tough act to follow. And while he was already a big guy, there was only one way to one-up him. Become even bigger. In "Batman v. Superman," we are introduced to a different kind of Batman, one who lives in a world of superpowers, aliens and gods. If he had any hopes of standing toe-to-toe with Henry Cavill's Superman – let alone take him on in a super-powered beat down – Affleck had to bulk up. A lot.

When all was said and done, Affleck ended up adding 30 pounds of muscle to his frame to pull off the cape and cowl. With a training focused on mass and strength, director Zack Snyder even went so far as to show a full training montage of Bruce Wayne in his batcave, just to prove any leftover naysayers wrong. The sequence, which featured squats, bench presses, weighted pull-ups and various crossfit exercises is a good taste of what Affleck had to go through in real life, but not nearly all of it. How was he able to do it all? The answer is simple. He's the Batman.

6 CAITY LOTZ

Caity Lotz White Canary

Before Katie Cassidy was called up to the major leagues of Star City crime-fighting, there was the first Black Canary: Caity Lotz. As Sara Lance, Lotz appeared on our screens as a reformed, highly-trained assassin and she made us all believe it thanks to her background in dance training and martial arts. While she has never divulged her fitness secrets, her Instagram account sometimes allows a sneak peek at what she has to learn and what she goes through to pull off those amazing moves of hers onscreen.

Now, Sara Lance leads a team of time-travelers in "DC's Legends of Tomorrow" and she is in better shape than ever. Her promotion from guest star to lead actor brought with it many new challenges and demands, the least of which was to justify her role as the deadliest woman in the Arrowverse. With a team that includes a nuclear man, a shrinking man, a metal man and a woman with the power of the entire animal kingdom itself, Lotz has earned her place as leader and she has the physical presence to back it up.

5 HENRY CAVILL

Henry Cavill as Superman

In "Man of Steel," Henry Cavill was to be the third actor to portray Clark Kent on the big screen. But after the Hugh Jackman days, Superman was a role to be approached like the ultimate hero that he was. A symbol of hope and the embodiment of strength, it almost seemed impossible to find someone to fill out those red boots, but director Zack Snyder had an ace up his sleeve, from his "300" days. A trainer to bring the super to the man, Mark Twight, who would almost become the unofficial "Justice League" trainer.

There is no denying it, Henry Cavill literally became Superman. He may not possess his powers, but he looked like he was ripped straight from the comic pages. Hours on end were spent in the gym, sometimes twice per day. Never once did he do the same routine twice, and never once did he give up. Consuming over 6,000 calories per day was just par for the course, and it helped him gain 20 pounds of pure muscle that allowed him to become a new Superman worthy to be at the forefront of the "Justice League."

4 SCARLETT JOHANSSON

Scarlett Johansson Black Widow

Black Widow was introduced to us as a secondary character in "Iron Man 2," and she was set to become a big part of the Marvel Cinematic Universe. As a deadly super-spy and assassin, the actress chosen would have to have a physique to match. In came Scarlett Johansson, who proved that any woman could stand back-to-back with the Avengers in a city overrun with aliens. If there was any doubt that she could pull off the skin-tight catsuit, her big action scene in “Iron Man 2” was enough to prove anyone wrong.

And yet, she didn't stop there. She doubled-down her efforts for "Captain America: The Winter Soldier," and after a pregnancy that side-lined her for stunt scenes during shooting for "Avengers: Age of Ultron," she came back without missing a beat for the demanding action scenes of "Captain America: Civil War." Not nearly enough is said about Scarlett Johanssen's physical work in the Avengers movies compared to the flashier, bulkier roles, and she just might be the unsung hero of the MCU.

3 CHRIS HEMSWORTH

Thor Chris Hemsworth Dark World

Standing tall at 6'3'', Chris Hemsworth put on 20 pounds of muscle to accurately portray the role of the God of Thunder, Thor. And with the results seen on screen, there is no denying the fact that the man could actually pass for a Norse deity. With the right amount of heavy-weight training and protein intake, Hemsworth completely transformed himself. In fact, the actor gained so much weight at the start of the first "Thor" movie that he reportedly was too big for his own costume.

After his breakout role as the hammer-wielding god, Hemsworth became one of the most popular actors in Hollywood and the People's Sexiest Man Alive of 2014. Like the people on this list who hail from the television medium, the Marvel movies can be seen as one big, cinematic television series. This means that time and time again, Hemsworth has to prove his mettle in the gym in order to be able to return to his Thor form every few years for the "Avengers" movies and his own sequels, "The Dark World" and the upcoming "Ragnarok."

2 DWAYNE “THE ROCK” JOHNSON

The Rock Hercules

Based on the "Hercules: The Thracian Wars" graphic novel from Radical Comics (written by Stephen Moore with art by Cris Bolsin), it was just a matter of time before Dwayne “The Rock” Johnson became a comic book movie star. Now sure, The Rock has always been a big guy. But even he knew the importance and relevance of the character. This new movie aimed to approach Hercules not as a demigod, but as a man whose legendary reputation preceded him. Naturally, Johnson  approached this role as a Herculean task all its own.

With training sessions of over 90 minutes and six to seven meals a day, The Rock clocked in at a reported 260 pounds. And these were no mere training sessions. Crazy sets and super-sets, with repetitions of 50 to even 75 when it came to the legs. Not shy about his work, The Rock proved a real hero when he offered his fans his full training routine and diet for the movie on his Instagram account, inspiring everyone to push as hard as he can.

1 CHRISTIAN BALE

Christian Bale The Dark Knight

At first glance, this might give you pause. Christian Bale is neither the bulkiest nor the longest-running comic book actor in this list, but nevertheless, on his utility belt, there is a notch that earns him the top spot on this list. You might have heard of this story before, but it still is worth repeating, and it is still so very impressive. After losing a shocking 60 pounds for his role in "The Machinist," Christian Bale had to climb himself back up from a weight of 121 pounds to 190 for the role of Bruce Wayne in "Batman Begins."

Not convinced yet? Well then it might be the time to mention that he only had 6 months to gain the weight back. While a lot of work had to be done in the gym to get the Bruce Wayne frame, the bulk of the work Bale had to accomplish took place in the kitchen, where he would have to eat in very high quantities. Compared to the steady evolution and transformations of many actors on this list, this one might not be the safest, but it sure is the most jaw-dropping. A training regimen of this intensity certainly seems like an accomplishment worthy of the Dark Knight himself.

Which actor transformations impressed you the most? Tell us your favorite (and maybe share your own workout routine) in the comments below!