Mark Wahlberg has opened up about consuming 11,000 calories a day to beef up for his role in forthcoming movie Father Stu.

The actor recently shared before-and-after photos of his progress over the course of three weeks in which he visibly lost muscle mass and gained more fat.

It was in preparation for his role portraying a professional boxer who becomes a priest named Father Stu.

Now, Wahlberg has told The Tonight Show Starring Jimmy Fallon that the dieting regime was “not fun”.

“Unfortunately, I had to consume, for two weeks, 7,000 calories, and then for another two weeks, 11,000 calories. And it was fun for about an hour,” he explained.

“It’s such a hard, physical thing to do. Losing weight, you just kind of tough it out – you just don’t eat, and exercise.

“And this, even when you’re full, I would wake up after a meal and have another meal. I was eating every three hours. It was not fun.”

The diet was strict and consisted of large amounts of protein.

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Wahlberg’s personal chef Lawrence Duran recently told E! Online: “His first breakfast is four eggs – that’s the pre-breakfast. Then, he does his workout and then after the workout, which is usually around 5 to 6 o’clock in the morning, we do eight eggs, six strips of bacon, a cup of rice, two tablespoons of olive oil and a protein shake. It’s his protein-inspired mass weight-gainer to help build on a little more muscle as well.

“Then, three hours later, we do some kind of ground beef or ground turkey, whether it’s been made into a hamburger patty or a meatloaf, with another cup of rice.

“And then, three hours later, I usually do half of a roasted chicken, another cup of rice, I’ll do about a cup of cooked spinach and a cup of cooked beets as well.”