It’s a weightier Vincent Cassel in ‘Mesrine’

Vincent Cassel finally got his Robert De Niro moment in the powerful two-part French gangster epic “Mesrine: Killer Instinct” and “Mesrine: Public Enemy No. 1.”

“I grew up watching ‘Raging Bull,’” says the 43-year-old actor, referring to the 1980 film for which De Niro won the Oscar for packing on the pounds to play boxer Jake La Motta. “It was kind of a fantasy [to put on weight for a role]. I thought maybe once in my life I would have to do that kind of transformation. And now it’s done.”

The tall, wiry Cassel gained 40 pounds for the second part of the movie about infamous French gangster Jacques Mesrine, who was gunned down in his car on the streets of Paris by the police in 1979. Because Cassel knew it would be impossible for him to shoot the first part as the younger Mesrine and then put on the 40 pounds as the older bandit, the film was shot in reverse order. So he took four months to gain the weight before the nine-month production began.

“I was helped by my doctors,” says Cassel, who won the Cesar, France’s equivalent of the Oscar, for his pulsating work as Mesrine.

“For the first time in my life, I had bad cholesterol. I was freaking out, but by the time I finished the movie, the weight was gone and so was the bad cholesterol. I actually had a problem keeping the weight on. I had an assistant coming with this huge milkshake every day. When we completed the first movie, which is the second part, I actually started to lose weight too fast and I had to stay on a certain kind of diet.”

The first part of “Mesrine” opens Friday with the second part following on Sept. 3.

Cassel, the eldest son of the late actor Jean-Pierre Cassel (“Army of Shadows,” “Murder on the Orient Express,” “The Diving Bell and the Butterfly”) and journalist Sabine Cassel, has made a name for himself both in French- and English-language films for playing heavies. Critics and audiences first took notice of him in Mathieu Kassovitz’s 1995 “La Haine,” in which he played a troubled youth living in the outskirts of Paris. He played the French master thief Francois Toulour in both 2004’s “Ocean’s Twelve” and 2006’s “Ocean’s Thirteen” and was a standout as Kirill, the out-of-control son of a Russian mobster living in London, in David Cronenberg’s 2007 thriller “Eastern Promises.”

But in person at the Standard Hotel on the Sunset Strip, Cassel is warm and friendly with sparking blue eyes and high cheekbones. He’s been married 11 years to his frequent costar, earthy Italian actress Monica Bellucci, and is a doting dad to their two young daughters. He calls the family “VIP Gypsies” because they are constantly moving among their homes in Paris, Rome, London and Rio de Janeiro.

“Mesrine” was a labor of love for Cassel, who was attached to the project for seven years. He explains that it took time to find the right director (Jean-Francois Richet) and writer (Abdel Raouf Dafri) and obtain about $50 million to make the four-hour film. “And it’s about an antihero that kills and gets killed by the police. It’s pretty political. We took the time to put it together. I really had time to infuse him. I met his girlfriends, his kids, some of his accomplices. I went to places where he had lived, plus the minute the movie was announced, I started to receive mail. Everybody had a story.”

There is a moment in the first part of “Mesrine” when the criminal emerges after a long time in solitary confinement from a Canadian prison cell and walks into the prison yard for the first time. Thin and scruffy and sporting an unkempt beard, Cassel looks like the spitting image of his father. “They say the day you lose your parents, you start to look like them,” he says.

And, in fact, Cassel had wanted his father, who died in 2007, to play Mesrine’s dying father in the film. But he passed away before shooting began. So he asked a family friend, actor Michel Duchaussoy, to play the father. When it came time to shoot the scene in which Mesrine visits his dying father in the hospital, Cassel was overcome with emotion, which spilled over into the film.

“The day we shot the scene it was terrible,” says Cassel, softly. “There was a tension on the set. We shot that really fast, maybe three takes. Then I shook his hand and said ‘Ciao.’”

Cassel has been working nonstop since he finished “Mesrine.” He will be seen this year in Darren Aronofsky’s “Black Swan” with Natalie Portman. The film is set to open the Venice Film Festival.

“It’s almost a horror movie,” he says. “I am kind of a Balanchine kind of character. I am the director of the New York City Ballet and I am the choreographer … and I use my sexuality to make my dancers work. I get involved sexually with them.”

He also reunited recently with Cronenberg and “Eastern Promises” star Viggo Mortensen for “A Dangerous Method,” set for release next year, which revolves around the relationship between leading psychologists Freud and Jung. Cassel plays a protégé of Freud. And he is also going to do a sequel to “Easter Promises,” which will be set in Russia.

Cassel also has several films in the pipeline to produce but doesn’t see himself stepping behind the camera to direct a feature. “I did direct two short movies,” he says. “I learned many things, and one of the things I learned was that I am not a director. It has to be visceral, and it’s not for me. I feel much more comfortable acting.”

susan.king@latimes.com