The celebrities who seriously upped their fitness game for a film

Celebrities from Chris Hemsworth to Blake Lively are renowned for upping their fitness game when it comes to training for a new film. 

We take a look at the stars who transformed their bodies and inspired us to hit the gym - click through for the full gallery... 

Blake Lively for The Shallows

"I was working out 13 hours a day because shooting was working out," the actress told Entertainment Tonight, explaining that because the thriller is set in the sea she spent a lot of time swimming and wading through waves of water.

Blake had welcomed baby daughter James with husband Ryan Reynolds a few months before filming began, and revealed that she found the challenge "neat".

She said: "It was neat to be able to do that, and it was neat to have that challenge after having a baby, because you think your body is so different – you think no matter what, it's never totally [going to] be the same."

Zac Efron for Baywatch

Zac Efron upped his fitness game as he trained with Dwayne Johnson for Baywatch, flooring fans with his incredibly muscular physique when he arrived on set. The star gave his Instagram followers a glimpse into his impressive training, which included tough exercises such as tyre flipping.

In one photo's caption, the High School Musical star confessed he had undergone "months and months of training for this moment" as he kicked off filming.

The actor also took to Twitter to share his strict healthy diet, admitting he had undergone a sugar and carbohydrate detox. "9 days of absolutely zero carbs & sugar. Only organic grass fed/free range protein and organic leafy greens," he wrote, before adding that "this lead to" a cheat day with an impressive menu. "Devoured a steak, 4 side potatoes/veggies, macncheese, 3 desserts, bread/butter, brick o cheese & caviar," he wrote.

Chris Pratt for Guardians of the Galaxy

Best known for his role as Andy Dwyer on Parks and Recreation, the actor set pulses racing when he posted a selfie on Instagram following one of his training sessions. Chris revealed that he had spent six months working out and changing his diet in order to get in shape for the Marvel film, flaunting the results of his hard work which saw him rocking impressive abs.

"I actually lost weight by eating more food, but eating the right food, eating healthy foods, and so when I was done with the movie my body hadn't been in starvation mode," he told People. "It wasn't like I was triggered to gorge myself and get really fat again."

He has since kept up his healthy lifestyle. "It's something that I think I can maintain because I don't spend four hours in the gym each day," he explained. "I do maybe one hour in the gym maybe four days a week, and that's it."

Jennifer Lawrence for X-Men: First Class

Trainer Dalton Wong worked with Jennifer Lawrence for the superhero film, and revealed that they would work out between 10-12 hours a day, with a series of exercises ranging from weight lifting to resistance training and squats.

"I could never live on a diet," Jennifer wrote in his book The Feelgood Plan. "Dalton taught me how to eat, move and live a delicious but healthy life. I will always thank him for that."

"We would do high intensity workouts in the mornings, such as cardio, and then relaxing stuff in the evenings like yoga," Dalton told Healthista. "Some days I would just take her to have a massage."

Chris Hemsworth for In The Heart of the Sea

Chris shocked fans when he unveiled his dramatic weight loss for the film, looking unrecognisable as he posed for a snap on Instagram. The actor had previously admitted he was prepared for the "pretty uncomfortable" process to achieving the look.

"We have to shoot the really skinny stuff where we drop down to five, six, 700 calories a day, a good three or four weeks," he told Entertainment Tonight. "And it's going to be pretty uncomfortable, but we'll be together in our misery."

However, the actor has since admitted he wouldn't embark on such a gruelling diet again, describing the experience as "too exhausting".

"I don't mind going up to Thor weight and then going back down to my normal body weight," he told Wonderwall. "It's easier to put it on than it is to take it off."

Daisy Ridley for Star Wars: The Force Awakens

Daisy was catapulted to fame as Rey in the latest instalment of the Star Wars franchise, but the star admitted that she upped her fitness game to get ready for the film. The British beauty told ELLE magazine that she would spend five hours a day, five days a week, training in the gym, while following a diet of "lots of fish, legumes and spirulina shakes."

The British beauty also wowed her Instagram followers with a candid glimpse into her gruelling workouts as she prepared to film Star Wars: Episode Eight, posting a short video which saw her undergoing tough exercises including weight-lifting.

"@gravyz12 has returned and #fridayfitness is here! Working on controlling the eccentric (slow on the way down) for injury prevention," she explained in the short clip's accompanying caption.

"For this week only this video features: me falling out of a press up, jack correcting my deadlift tekkers, me and him having a DMC during spider bicep curls and a post workout ice bath. THAT'S how I get through work outs, lots of chat to distract me from the pain!#GAAAAAAINZ #toostrongfortoolong #likemaryjbligesaid."

Daniel Craig for Casino Royale

The British actor set pulses racing when he made his debut as James Bond in 2006, turning heads with his muscular physique.

Trainer Simon Waterson, who helped Daniel get in shape, revealed that he was particularly impressed at the actor's dedication when it came to switching up his lifestyle and getting toned.

"After a few months of training, Dan was lifting and performing like an athlete," he told GQ. "He had full focus on what he wanted and the discipline from me to help him execute it. Even now, I still can't believe the physical changes he achieved. It just shows that with will power and dedication you can achieve anything."

Daniel later admitted he struggled to keep up the fitness routine, and found himself once again upping his game when he filmed Quantum of Solace. "I needed to get as fit as I possible could," he said at the time. "Although I was big and muscled last time, I was actually not as fit as I am now."

Jake Gyllenhaal for Southpaw

Jake's tough workout routine for the film included doing 2000 sit-ups a day – and the actor wowed fans when he hit the screens with his transformed figure.

Director Antoine Fuqua admitted that he had urged Jake to train 'like a fighter' in order to play the role more convincingly, including working out over six hours a day.

"I said, 'Jake, you have to train like a fighter. I can't have you fake it'," Antoine said, recalling a conversation with the actor where he agreed to undergo the same regime to keep Jake motivated. "'You have to be in a gym, twice a day. Even on Sundays.'"

The gruelling training lasted for five months, and included everything from push-ups and core training to lifting an oversized tyre – Jake reportedly gained 15lbs purely in muscle due to the intensity of his workouts.

J.K Simmons for Justice League

The Whiplash star caused a social media meltdown when photos of him surfaced on Instagram during his training for his upcoming role in the new Justice League film, where he plays Commissioner Gordon.

J.K.'s personal trainer Aaron Williamson posted photos of the actor during their workouts on the social media website, and revealed he had "so much respect" for the actor whom he admired for his dedication.

"Every time we train together I forget he's 61 years old," Aaron captioned one of the behind-the-scenes snaps. "So much respect for this guy. #JKSimmons #OldManCranking (hash tag via @mountaindog1)."

Natalie Portman for Black Swan

Natalie took home the Oscar for Best Actress following her role as the troubled ballerina - and the star spent months preparing for the performance. Under the guidance of New York City Ballet dancer Mary Helen Bowers, Natalie worked for up to eight hours a day, training six days a week with a series of exercises from cross-training to endurance exercises.  

"Ballerinas have obvious physical qualities like long, lean muscles and beautiful posture," she told Shape. "We wanted her to look the part, but we also wanted to make sure she was able to move and dance like a professional ballerina."

Swimming also proved to be key to Natalie's impressive regime. "We usually started by swimming a mile a day, doing the front crawl and breast stroke," Mary Helen explained. "Then we'd do 2 hours of ballet exercises and resistance work."

Will Smith for Ali

The Fresh Prince of Bel Air star had jaws dropping to the floor when he transformed his body for the 2001 hit film about boxer Muhammad Ali, in which he played the leading role. The actor went from 185lbs to an impressive 220lbs, using a combination of intense boxing, weight lifting and bench-pressing exercises.

He also followed a high carbohydrate and protein diet, alongside training six hours a day, five days a week to physically prepare for the challenging role.

Will himself credited director Michael Mann for encouraging him to stick to the new routine. "He laid out what the days would be like, he laid out the food that I was going to eat," Will revealed at the time.

He added: "He laid out the process of becoming Muhammad Ali physically and how that physical process would natural lead to a comprehension of the mental and emotional position that Muhammad Ali lived in and how that mental and emotional space would automatically help me understand the necessity for the spiritual strength."

Zoe Saldana for Guardians of the Galaxy 2

Returning to set for the second instalment of the Marvel film, Zoe Saldana proudly flaunted her post-pregnancy body as she tried on her old costume from the first film which she shot in 2013. Zoe, who has since given birth to adorable twin boys Cy and Bowie, took to Instagram to reveal show off the results of her hard work in a snap of herself back in the outfit.

"You guys, I had to share this," she excitedly wrote in the caption. "This is one of the old #guardiansofthegalaxy costumes that I wore back in 2013. After twins, I can't believe I was able to slip into this."

The Avatar actress also had a message of encouragement for new mums working to stay in shape. "It pays off to work hard!" she added. "I mean it mommies of the world, if I did it you can too."