How Actors Transform Their Bodies for Roles

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Photo Source: “Thor: Love and Thunder” Credit: Jasin Boland

Whether it’s Chris Hemsworth going beast mode to portray Thor in the Marvel Cinematic Universe, or the already-svelte Natalie Portman losing 20 pounds to portray an obsessive ballerina in “Black Swan,” actors are often asked to drastically transform their bodies for roles—and in the blink of an eye, at that. We talked to personal trainer Gunnar Peterson—whose vast celebrity client list includes Dwayne “The Rock” Johnson, Busy Philipps, Billy Dee Williams, and the full roster of the Los Angeles Lakers—to get the inside scoop on the individualized fitness and nutrition plans needed for actors to quickly and safely alter their physiques for a specific character.


How do actors get in shape so fast?

It's Always Sunny in Philadelphia“It's Always Sunny in Philadelphia” Credit: Patrick McElhenney/FXX

For most of the population, getting in shape means gradually building good eating and exercise habits and aiming for consistency. However, actors don’t always have the luxury of time if asked to change their bodies to perform a specific character—a request that should always be made clear well in advance of contract negotiations. Furthermore, the transformations you see from stars working with big-budget studios aren’t the result of a realistic timeline for someone without that support system. If you ever catch yourself comparing your gains, losses, or otherwise to theirs, remember this wonderfully sarcastic Instagram post from Rob McElhenney, who bulked up for the 13th season of “It’s Always Sunny in Philadelphia.” 

“Look, it’s not that hard,” McElhenney wrote. “All you need to do is lift weights six days a week, stop drinking alcohol, don’t eat anything after 7pm, don’t eat any carbs or sugar at all, in fact just don’t eat anything you like, get the personal trainer from Magic Mike, sleep nine hours a night, run three miles a day, and have a studio pay for the whole thing over a six to seven month span. I don’t know why everyone’s not doing this. It’s a super realistic lifestyle and an appropriate body image to compare oneself to.” 

RELATED: How to Act Sick for a Role 

To turbocharge the process, actors might:

Tailor their diets

Many actors trying to change their body for a role will work with a nutritionist and personal chef to ensure their diet matches their goal. Generally, the diet that best supports an intensive exercise regimen includes complex carbohydrates from whole grains, legumes, fruits, and vegetables; healthy unsaturated fats found in nuts, seeds, and avocados; and lots of lean proteins low in saturated and trans fats (bring on the chicken and fish!). 

Count calories

A diet’s calorie count should be tailored to specific objectives. If someone wants to bulk up, they need to eat at a surplus; if they want to lose weight, they must eat at a deficit. For example, to get Thor’s god bod, Chris Hemsworth ate 4,500 calories per day—more than double the 2,000 calories recommended by the Food and Drug Administration for the average consumer. But to portray a shipwrecked sailor in “In the Heart of the Sea,” the actor reduced his caloric intake to a mere 500 calories per day.

Of course, extreme caloric deficit can be very dangerous. According to endocrinology, diabetes, and metabolism specialist Dr. Louis J. Aronne, a crash diet risks leaving you dehydrated and with dangerous blood sugar spikes and drops. It causes your muscles to break down, including the muscles in your heart—which can lead to ventricular arrhythmias and even death. That’s why he and other medical professionals recommend losing no more than approximately 1 percent of your body weight in a week. Be sure to consult with a medical professional before going into caloric deficit. 

Track macros

It’s important to keep track of carbs, fat, and protein macros, especially since when it comes to building muscle, protein is king. The recommended daily allowance for protein is between 0.31 to 0.45 grams per pound of body weight, but many nutritionists and bodybuilders recommend bumping that up to 0.8 to 1 gram for those trying to gain and maintain muscle. 

Work out

The next key to the fitness puzzle is exercise, usually a mix of weightlifting and cardio. While Peterson recommends both, he emphasizes the importance of weight training: “Don’t wait on the weights,” he says. “Oftentimes people start with cardio…and then add weight training. I would recommend starting with a combination of both,” along with a focus on nutrition and recovery. 

  • Lift weights: If an actor is supposed to look stronger quickly, workouts tend to be more focused on weightlifting. Kumail Nanjiani pumped a lot of iron to gain viral-worthy muscles for his role as Kingo in “Eternals.” His exercise plan, created by trainer Grant Roberts, involved intense hour-long bodybuilding workouts to exhaustion, five days a week. And to put on 20 pounds of muscle for his role as a family man turned prison gangster in “Shot Caller,” Nikolaj Coster-Waldau worked with personal trainer Jesper Mouritzen to create a modified take on the Charles Bronson prison workout: handstand pushups, regular pushups, situps, squats, squat thrusts, prison burpees (a burpee with one-legged pushups added in just for fun), star jumps, and step-ups. 
  • Do cardio: Alternatively, if an actor needs to look more slender than buff, or if they have more time to train, the exercise plan might include more cardio. When Chadwick Boseman wanted a wiry, feline appearance for his role as the MCU’s Black Panther, he combined lighter weight training with multiple martial arts workouts


Ah, the best part: sleep, glorious sleep. Sleep affects both diet and exercise, so anyone trying to get in shape fast should aim for at least seven hours of sleep per night. Not only can sleep deprivation lead to overconsumption since sleep impacts the neurotransmitters that indicate when to stop eating, but lack of sleep also interferes with muscle recovery and reduces energy. Alternatively, proper sleep helps regulate eating, encourages muscle growth, and provides enough energy to hit the gym yet again. 

Get support

Personal trainers, nutritionists, and chefs, oh my! Whether actors are trying to maintain a sleek physique or are going for a total body transformation, they rely on their team of experts to help. Even the most disciplined actors benefit from a personalized plan of action, nutrition-packed food, and the external motivation to give that last rep their all. 

“I would not have been able to do this if I didn’t have a full year with the best trainers and nutritionists paid for by the biggest studio in the world,” Nanjiani wrote on Instagram. “I’m glad I look like this, but I also understand why I never did before. It would have been impossible without these resources and time.” 

Fitness expert and founder of Nerd Fitness Steve Kamb agrees that an actor’s support team is a significant part of their body transformation success. “You’re looking at a guy who had seven months to train for this role and had a personal trainer, strength coach, stretching coach, masseuse, yoga coach, and more,” he writes of Brad Pitt’s muscle gain for “Troy.” Studios will often pay for these support teams if requesting a body transformation for a role.

Of course, there’s no one-size-fits-all when it comes to changing sizes. Peterson says that he customizes new workouts for every client. “There are a number of factors to consider with each person, so the cookie cutter approach will always fall short,” he says. Across the board, the trifecta of proper diet, regular exercise, and good sleep—especially when supported by a team of experts—helps actors achieve their physique goals fast. “The closer you get to your goal, the more important nutrition is. Recovery is the sleeper—all puns intended—and it is an absolute must as you zero in on your goals.” Above all, consistency is key. “Get a system in place that is smooth and efficient and don’t second guess it,” he advises.

Actors who lost weight for roles

Mila Kunis“Black Swan” Courtesy Fox Searchlight

As shown by this list, restricting caloric intake is the key to losing weight fast for roles—but it comes at a steep price. Those aiming for a hasty weight loss transformation often eat what many nutritionists warn is a dangerously low amount of calories per day. The National Institute for Health emphasizes that rapid weight loss “can cause you to lose muscle, water, and bone density,” which can cause permanent damage to your body.

It’s essential to understand that dramatically losing or gaining weight for a role is not the norm, nor is it a requirement to be an actor. Although the following actors chose to put their bodies in danger by losing weight quickly, many other actors, such as Jennifer Lawrence and Florence Pugh, refused to lose weight for a role—and still landed the part. 

  • Christian Bale: When he lost a shocking 63 pounds for the role of a mentally ill insomniac in “The Machinist,” Bale took caloric deficit to the extreme, consuming only an apple, a tin of tuna, and black coffee to the tune of 200 calories a day for the four months leading up to production. 
  • Tom Hanks: To portray a man living with AIDS in “Philadelphia,” Hanks lost around 30 pounds by eating 1,000 daily calories and then burning them off by doing 1,000 calories’ worth of cardio. He underwent another major body transformation that same decade by losing 55 pounds in four months for his role in “Cast Away.” 
  • Michael Fassbender: In the appropriately titled “Hunger,” Fassbender lost 40 pounds by eating only 900 calories per day to portray an IRA hunger striker.
  • Mila Kunis: For her role in “Black Swan,” Kunis lost 20 pounds in five months. She subscribed to a food service and exercised multiple hours a day, every day, to achieve her lissome ballerina figure.

Actors who gained weight for roles

Christian Bale“The Dark Knight Rises” Courtesy Warner Bros. Pictures

Whether it’s getting ripped fast or cultivating mass, getting heavier with haste means a lot of eating. Here are some of the actors who successfully increased their size.

  • Christian Bale: The king of body transformations, Bale packed on more than 30 pounds of muscle to portray Batman in “The Dark Knight” and “The Dark Knight Rises.” He also gained 40 pounds to portray former Vice President Dick Cheney in “Vice,” attributing his weight gain success to eating a lot of pies.
  • Vincent D’Onofrio: For his role as overweight army recruit Gomer in “Full Metal Jacket,” D’Onofrio gained 75 pounds. His breakfast alone “consisted of steak, three eggs, a half loaf of bread and a quart of milk.” 
  • Brad Pitt: Pitt took seven months to gain 25 pounds of lean muscle when he was cast as the ripped hero Achilles in “Troy.” He ate a surplus of nutritious foods, especially chicken, broccoli, and brown rice, and lifted to progressive overload. 
  • Hilary Swank: Swank spent several hours training and lifting weights six days a week to gain the 19 pounds of muscle necessary to portray a boxer in “Million Dollar Baby.” 
  • Alicia Vikander: Working with trainer Magnus Lygdback, Vikander added 12 pounds of muscle to play Lara Croft in “Tomb Raider.” Her routine included a protein-heavy diet and weightlifting workouts over seven months. 

Medical advice disclaimer: Content in this article is provided for informational purposes only, and does not intend to substitute professional medical advice, diagnosis, or treatment.

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