Beefing up for a role definitely gets Hollywood talking — just ask Jake Gyllenhaal, who had to turn into a hulk-like warrior for his role in ‘Prince of Persia.’ In an interview with Moviefone, he admitted that putting on all that muscle wasn’t that big of a deal. “There was nothing hard about it, man, I was paid to get in shape,” he said. Easier said than done, Mr. Gyllenhaal.

But were rigorous training and a strict diet the only factors contributing to his new washboard abs? Gyllenhaal’s trainer, Simon Waterson, spoke with PopEater to reveal how the doe-eyed actor transformed his body in less than four months.

Gyllenhaal’s ‘Prince of Persia‘ trainer is a former Royal Marine who has helped other A-list actors — including Pierce Brosnan and Daniel Craig for the ‘James Bond‘ films — bulk up for movie roles. But turning Gyllenhaal into a hulking warrior took a lot of mental and physical stamina; Waterson admits the average person would have to be “extremely dedicated” to achieve similar results.

In the early morning, Gyllenhaal would put on a 20-pound flak jacket and run around a park and in the sand — simulating scenes he would be filming in Morocco for ‘Persia.’ He’d then head off to script readings and sword fight training before returning in the evening to start his second round of exercise, resistance training. The actor would eat six times a day — three meals and three snacks, each of which contained a lot of protein, electrolytes and carbohydrates.

“He had the luxury of having me around 24/7 for almost a year and even while he was filming,” Waterson says. “I made sure he trained when he need to train. He was fed when he needed to be fed. And rested when he needed to rest. You have to bear in mind, this was an intensive four months of training. He was living an athlete’s life.”

Waterson admits anyone could get Gyllenhaal’s shape, but should go about it in a less-intensive way. “The average person isn’t going to be climbing walls and running through sand wearing a suit of armor. Jake had to be conditioned in a way of being capable of doing those things while cameras were rolling hours a day on set,” he said, adding that his focus was to get the actor in such great shape that he could withstand the rigorous stunts and months of filming without getting injured.

Waterson says the average person should consult with a personal trainer and make sure their body can endure the process before tackling Jake’s ‘Persia’ regimen. He adds the most people probably “don’t have the time” to commit the same way Gyllenhaal did, and advises people looking to get in shape fast to do hard cardio workouts one day and resistance training the next day.

Even at his peak, Gyllenhaal had a few moments of weakness, like anyone else. “Like anybody, you always have a little bit of self doubt,” Waterson said. He did every exercise with Gyllenhaal. Set for set, rep for rep and mile for mile, he helped push the actor — even when there were intense moments of throwing in the towel.

“He was 110 percent committed. And I think I trained him too well, because he was a lot fitter than me by the end of it,” Waterson jokes. “I have to give Jake a lot of the credit. Yes, I was his trainer, but for this part, he was very disciplined. I have a massive respect for him because at the end of the day, he is an actor and very committed to being the best.”

While Waterson couldn’t be prouder of Gyllenhaal, he has moved on to his new project — another A-list celebrity, whom he wouldn’t reveal, but said would be bulking up over the few months. “You’ll have to wait and see, but I think people will be extremely surprised when they see how much muscle this guy has now,” he reveals.

Jake Gyllenhaal’s ‘Prince of Persia’ Regimen

? Pre-workout Snack: Half a banana, some nuts and an espresso.

? Morning Workout: An hour-and-a-half cardio workout while wearing a 20 lb. flak jacket to simulate the weight of armor. Interval training (10 minute uphill sprint, followed by abs exercises). Repeat sequence five times, then a 10 minute run, followed by stretching.

? Breakfast: An egg-white omelet, a small protein shake and an isotonic drink to replenish salts lost during training.

? Lunch: Baked potato with tuna and salad.

? Evening Workout: An hour of resistance training using cables to simulate sword fights; pull-ups, press-ups, abs exercises using weights; finish with stretching.

? Dinner: Soup and a protein shake

? Snacks/supplements: Two liters of water, protein bars, dark chocolate, supplements rich in omega-3, 6 and 9. No foods containing refined sugar, occasional glass of wine allowed.