Mark Wahlberg in The Fighter

Smack in the middle of Mark Wahlberg’s cavernous home gym here, amid the racks of weights and rows of cardio equipment, is the emblem of a career-long ambition: a regulation-size boxing ring. For as long as he has been a movie star, Wahlberg, 38, has wanted to play a boxer. He has come close a few times. He had the lead role in a never-made biopic of the middleweight champion Vinnie Curto and was briefly attached to The Black Dahlia, the mystery noir whose hero is an ex-pugilist. Wahlberg now finally has a boxing movie in the can, and the bonus is that it’s an especially personal one. The Fighter, of which he is also a producer, tells the life story of the Lowell, Mass., boxer “Irish” Micky Ward, one of his childhood heroes.

Wahlberg has been training for The Fighter for more than three years. Wahlberg said it was important for him to show “the most realistic boxing ever in a film,” which meant sparring with real fighters. The general idea: “Let’s try not to kill each other, but definitely get in there and take some shots.”

He gained nearly 30 pounds for a handful of scenes filmed in March that show a retired, out-of-shape Ward. When feedback from a rough-cut screening suggested a few more close-ups for the climactic fight, Wahlberg had to lose that extra weight quickly — hence a stepped-up training regimen and a strict low-carb diet.

reunion with russell

As Wahlberg would be the first to admit, he now has an acting and producing career that few could have foreseen back in the mid-’90s when the rapper, teen idol and underwear model known as Marky Mark decided to reinvent himself in Hollywood. “I feel like I’ve snuck in the back door,” he said.

This year Wahlberg has an eye on both the summer box office and the awards season. The Fighter, which reunites him with the director David . Russell, who steered him toward two of his most affecting performances, in Three Kings and I Heart Huckabees, is ready for a year-end release. But first, he further develops his comic persona, on view in Date Night, in The Other Guys, a buddy-cop action spoof in which he and Will Ferrell play New York Police Department underachievers.

It was Russell, a close friend of Wahlberg’s, who introduced him to Adam McKay, the director of The Other Guys. “Mark has a great capacity for comedy,” Russell said, “but it’s a comedy that comes from being very real and intense.”

wearing a straight face

Wahlberg is the rare actor who’s at ease in both maximalist and minimalist modes. He can be compelling while acting up a storm (a hotheaded detective spewing salty tirades in The Departed, a conscience-stricken firefighter ranting against petro-capitalism in Huckabees) or when seeming to do very little (the most famous scene in Boogie Nights, in which a drug deal messily unravels, peaks with a nearly minute-long close-up of his dumbfounded expression).

In either case his great gift as an actor is his straight face. He wears it not as a mask of deadpan irony but as a mark of deep sincerity, which can be a source of comedy or pathos, sometimes both at once. He doesn’t often get to stretch, and he has played more than his share of cops and criminals (“I’m still waiting for a call for an English period piece,” he said). But he is almost without fail the most convincing thing about any movie he’s in.

The winning directness that is now Wahlberg’s hallmark is perhaps the flip side, or the grown-up version, of the keep-it-real imperative that guided him as a rapping homeboy and, before that, as a teenage thug in working-class Boston. (He spent six weeks in jail for assault when he was 17.)

enacting life

Wahlberg has not shied from roles that echo his troubled past. Writer-director James Gray said that for The Yards, his drama about corruption among Queens subway contractors, he had asked Wahlberg to play the smooth operator Willie (a role that eventually went to Joaquin Phoenix), but Wahlberg wanted the less showy part of Willie’s childhood friend Leo, an ex-convict. “He knew the fear and the insecurity and the desire for redemption,” Gray said in an e-mail message, adding that Wahlberg’s best work “always reflects a life that is lived.”

“For a long time I’d been acting in my life anyway, whether conning my way into something or out of something,” he said. “I was always a fairly good salesman, and a fairly bad liar, so if I believed it, I could do a good job of convincing somebody else.”

Increasingly the rising-star exploits that inspired Entourage, the popular HBO series he produces, also seem to come from a previous life. Wahlberg described himself as above all a devout Roman Catholic, a devoted husband and father of four. “The first thing I do every day when I leave my house,” he said, “I go to church, man, get down on my knees.”

The buddies who inspired the characters in Entourage are still in his life — he often practises his lines with them — but the only entourage in evidence at the Wahlberg residence that day was a small contingent of maids and nannies.

most prepared

Wahlberg’s producing career continues to flourish, the latest being Boardwalk Empire, a series about Atlantic City in the 1920s, with a pilot directed by Martin Scorsese. But no amount of success — not even the Oscar nomination he received for The Departed (best supporting actor) — has made him feel fully at home in the industry. His work ethic is bound up with the sense that he still has something to prove. “I appreciate every opportunity I’ve been given,” he said. “I want to show up early. I want to be the most prepared.”

Preparation is an inadequate word for the Herculean effort that has gone into The Fighter, a passion project that has an air of autobiography. “There’s a lot Micky and I have in common: our willingness to work hard, to do whatever we have to do to achieve our goals,” Wahlberg said. He described the film as a tribute to his and Ward’s shared origins, a story about “that world and how difficult it is to make it out of there, and how important it is to people to have somebody to root for.”

Gray recalled that while making The Yards, he often found Wahlberg rereading pages that had already been shot. Gray said that when he pointed out they had moved on to other scenes, Wahlberg would “look at me like I was nuts.” His response had the ring of a credo: “Jim, I always need to know where I was, and where I’m headed.”

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