November 2, 2026, 7:34 pm | Read time: 5 minutes
With the film “Verity” and the series “Below,” Josh Hartnett makes a comeback with a double punch. Many fans are likely relieved, feeling that the Hollywood star takes too long between projects. The 48-year-old already has nearly 30 years of Hollywood experience! During this time, various roles have demanded not only acting talent but also physical skills and transformations. FITBOOK looks back at Hartnett’s most physically demanding roles.
In “Verity,” Hartnett must win over fans of the book. For “Below,” he had to master a specific Canadian dialect, obtain a boating license, and learn other skills to convincingly portray an experienced fisherman. Hartnett’s entire filmography is as diverse as these roles. The actor constantly tried new things and wasn’t afraid to push physical limits. He underwent military drills to play a soldier, engaged in months of intense professional boxing training, and underwent targeted weight transformations.
From High School Athlete to Actor
Perhaps his passion for physical challenges was innate. In Hartnett’s youth in Minnesota, everything pointed to a career in competitive sports. He grew up in the U.S. state of Minnesota and was a celebrated football player in school. As he shared in an interview with “The Guardian,” a severe ACL injury abruptly ended his sports aspirations.
This setback eventually led him to the school theater group, where he auditioned for a play about Tom Sawyer and landed the role of Huck Finn. Thus, the athlete became a passionate actor. Not long after, more opportunities arose. His first projects listed on IMDb date back to 1998. At that time, Josh Hartnett was 20 years old and had just finished school. From there, his rise in Hollywood gained momentum. In 2001, he appeared in two blockbusters: “Pearl Harbor” and “Black Hawk Down.” In both films, he played a soldier, with the preparation for the first film being particularly demanding.
Drill Camps for War Epics: “Pearl Harbor” and “Black Hawk Down”
For his breakthrough in the blockbuster “Pearl Harbor,” Hartnett, along with co-star Ben Affleck, completed a four-day, extremely challenging military boot camp. He was also supported by Dutch celebrity chef and trainer Jørgen de Mey, who published a book about his work with Hartnett, Affleck, and other stars.1
In an interview with “GQ,” he said that the preparation for the wartime romance film was surprisingly intense, especially compared to the pure war drama “Black Hawk Down” directed by Ridley Scott. The boot camp for “Pearl Harbor” took place in the mountains of Hawaii, which initially sounded “nice” to Hartnett. But the reality was different. “We had this staff sergeant, Sergeant Donnelly, who hated being assigned to watch over us actors. And he made our lives hell for a week,” Josh Hartnett recalled about that time.
Some didn’t fare well because they had to run so much in the camp. Hartnett revealed, “We did so many things that went far beyond what insurance would allow today.” Looking back, he doesn’t know why director Michael Bay wanted them to undergo such an intense boot camp for “a romance film.” But: “We got through it and ended up growing closer as a team.”
“Black Hawk Down” also required precise military training to convincingly portray soldiers in war. For this, Hartnett and his colleagues worked with real Rangers, Delta Force members, or pilots on actual U.S. military bases, depending on their roles. Hartnett played Ranger group leader Staff Sergeant Matt Eversmann and completed an introductory course at Fort Benning. A tough preparation that paid off. The war drama is still praised today for its realistic portrayal.2
Months of Boxing Training: Strict Weight Control for “The Black Dahlia”
For his role as police officer and ex-boxer Bucky Bleichert in the thriller “The Black Dahlia” (2006), Hartnett’s former mindset as a football player certainly helped. Instead of military exercises and missions, he had to immerse himself in a specific sport: boxing. As “GQ” reported in 2006, the then 28-year-old trained for months at the renowned boxing gym “Circle of Discipline” in Minneapolis and maintained a strict diet to keep his target weight of exactly 175 pounds (about 79.5 kilograms). He also used this boxing preparation for the boxing drama “Resurrecting the Champ” (2007).
30 Pounds Plus for “Oppenheimer”: The Unhelpful Advice from Matt Damon
For Christopher Nolan’s Oscar-winning epic “Oppenheimer” (2023), Hartnett once again showed courage for physical transformation. To convincingly portray the historical Nobel laureate Ernest Lawrence, Hartnett deliberately gained around 30 pounds (about 14 kilograms).
Only on set did he receive well-intentioned but late advice from co-star Matt Damon. On “The Tonight Show” with Jimmy Fallon, Hartnett shared: “He told me not to gain as much weight as I had already done for the role. I had already gained about 30 pounds (about 14 kilograms) for the role, and he just said, ‘You’ll never lose it, kid.'”
However, Damon’s warning proved unfounded, as Hartnett’s current appearances in “Verity” and “Below” show. Especially in the series “Below,” the 48-year-old appears strong and fit.
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Dietary Change: From Vegetarian Back to Meat Consumption
At the age of twelve, Hartnett chose a vegetarian lifestyle after encountering a tumor while cutting up a chicken for his mother. He revealed this in an interview with the animal rights organization PETA, which awarded him the title of “Sexiest Vegetarian Alive” in 2003 for his meat-free diet.
During the physically demanding filming of “The Black Dahlia” in Bulgaria, however, his body reached its limits. A Bulgarian doctor diagnosed Hartnett with anemia and advised him to eat meat again to meet the high nutrient and calorie demands of the intense boxing training and long workdays.3
Today’s Fitness Secret: Country Life in Hampshire
Today, Josh Hartnett lives with his wife, British actress Tamsin Egerton, and their four children on a rural estate in Hampshire, England. Instead of rigid gym routines, Hartnett takes care of his animals every morning—including pygmy goats, chickens, and guinea pigs—and stays fit naturally through rural family life.