Mark Wahlberg went all in for his latest role. ET’s Cassie DiLaura spoke to the 50-year-old actor ahead of the release of “Father Stu”, for which Wahlberg put on 30 pounds in six weeks to play Father Stuart Long, the real-life boxer-turned-priest.

“I had six weeks to put on about 30 pounds. I started with 7,000 calories for the first two weeks and then 11,000 calories for the final four weeks,” Wahlberg said. “None of it was fun, except for the first meal was amazing, because I hadn’t eaten anything up until that point. But after that, when you’re already full and you have to eat again, and at my age it’s just not a healthy thing to do, to try to put on that kind of weight in that amount of time.”

After enjoying his first weight-gaining meal, the process quickly grew tiresome and unenjoyable, especially given the fact that he was literally drinking olive oil by the glass as part of his daily routine.

“I wasn’t eating anything that you would think, ‘Oh my God, I get to sit on the couch and eat ice cream and pizzas,'” he explained. “… I tried to do it in a healthy way. It was a dozen eggs and a dozen pieces of bacon, two baked potatoes, a Porterhouse steak, two bowls of white rice, and a glass of olive oil. The first two weeks were high proteins. The second two weeks were a lot of carbs. The last two weeks starches, and then sodium, just to kind of get as bloated as possible. So not a lot of fun.”

Though he had to put on weight, Wahlberg didn’t give up his morning workout routine, instead using it to help him get hungry enough to consume the necessary amount of calories.

“I had to get up the appetite, so I would go in there and try to lift as heavy as possible just to get hungry,” Wahlberg told ET. “And then I’d have the weight gainer shakes as well and all that stuff. But none of it was fun. There’s nothing worse than when you’re full from the last meal and you have to eat again.”

Like his physical transformation, getting the film made was a challenge. Wahlberg, though, made sure he, “never gave up hope and continued to push the ball up the hill until we were able to make the film.”

“I was obviously very thrilled with the results… Making it a kind of down and dirty, gritty, independent way was much better, because… that’s who these people are,” he said, adding that he reached out to his co-star, Mel Gibson, for advice as he worked to get the project made.

“When I was talking about making this film, I knew that Mel had made ‘The Passion of The Chris’t, and I really admired what he was able to do with that film. He financed it himself. It was his love letter to God,” Wahlberg said. “And so I picked his brain quite a bit when we worked together on ‘Daddy’s Home 2’… He wanted to be a part of telling the story.”

In the end, it was worth all of his hard work, as it was a way for Wahlberg to share his faith with the world. Father Stuart Long’s inspiring journey from self-destruction to redemption was also something that Wahlberg related to.

“We both had very difficult childhood upbringing, both kind of searching for our calling, and, I think, both kind of getting to a place where we wanted to do more good and serve God, and certainly appreciating all the blessings that have been bestowed upon me,” Wahlberg said. “… Now having me continue to echo his message and take that responsibility on myself after the film is over to continue to do more substantial work, and continue to bring people together and promote a message of hope and faith.”

While Wahlberg is passionate about sharing his faith, it’s not something he pushes on his four kids, Grace, 12, Brendan, 13, Michael, 16, and Ella, 18, whom he shares with his wife, Rhea Durham.

“It’s a tricky thing with my faith. I wanted my kids to get a Catholic education, but I don’t want to impose going to church on them and all that stuff. I just want to be an example,” he told ET. “For them to see that Dad can’t miss church, or can’t miss prayer time, can’t miss his daily devotional, and just my routine as a whole, that hopefully, one day when they’re kind of trying to figure it out, they’ll realize, ‘Well, that thing works for Dad. Maybe it’s worth trying.'”

“But I don’t want to force them to do it, because I think they may resent it and push back,” Wahlberg continued. “So, I’m just trying to be an example and show them that it works for me in all the good things that have happened in my life, including them and their mom, has been provided to me by God, when I was prepared for it and ready for it.”

Instead of imposing his faith on his children, Wahlberg said that he tries “to be an example” that they and others can look up to.

“Trying to show kids in inner cities growing up, like the ones that I did, that anything is possible as long as you’re willing to go out there and do the work. And really just trying to encourage people to do their best, to be their best,” Wahlberg said. “I think being so blessed and so fortunate and having been able to turn my life around the way that I did, it certainly wasn’t to forget about where I came from. It’s about giving back and hopefully, through this, starting to do more meaningful things.”

“Father Stu” will hit theaters April 13.

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