See Wahlberg's 20-pound weight gain for the upcoming movie: It's "just as hot in person," says the producer-star's wife.

Mark Wahlberg went from muscle daddy to dad bod in three weeks for his new movie Stu.

The Oscar-nominated actor showed off his drastic transformation for the reality-based movie on Instagram, sharing side-by-side photos of his 20-pound weight gain for the role of a man who plays many roles throughout his tumultuous life, including a boxer, an aspiring actor, and a priest after suffering a tragic accident.

Wahlberg, 49, previously shared a video of himself pushing out his stomach, confirming that he's "up about 20" pounds and "inspired to be better" for "a role."

Wahlberg's wife, Rhea, commented under the post, writing that the actor's new body "looks just as hot in person."

"We're back in the boxing ring. There's a bit of boxing in the movie," he told Jimmy Kimmel in April. "I'm playing a guy who was a fighter, he was many things; He was a fighter, he moved to L.A. to become an actor, he fell in love with a girl, he kind of had an accident, he had an out-of-body spiritual experience, he decided to become a priest, he died of a rare disease, IBM, but he had a big impact on a lot of people in a very short amount of time. So, it's quite the story and quite the journey."

The producer-star explained that his training involved putting on as much weight as possible over the course of the film, after the initial round of scenes where the titular character attempted a boxing career.

"I'm challenging myself to put on 30 pounds in the next six weeks," he said, adding that his first meal to put on the pounds would be a 20-piece chicken nugget and hot wings from Kentucky Fried Chicken and a six-pack of beer. "I actually have someone who's consulting, they want me to do it as healthy as possible."

Wahlberg's dad bod transformation follows the social media quake Will Smith caused when he posted a photo of his own dad bod reveal Sunday on Instagram.

"I'm gonna be real wit yall - I'm in the worst shape of my life," Smith captioned the image on Instagram.

See Wahlberg's transformation for Stu — directed by Rosalind Ross and co-starring Mel Gibson and Jacki Weaver — above.

Hear more on all of today's must-see picks, plus Danielle Panabaker on this week's episode of The Flash, in EW's What to Watch podcast, hosted by Gerrad Hall.

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