'He is a brilliant con artist, OK?" Christian Bale says of Irving Rosenfeld, the character he plays in American Hustle. "But, really, who is he conning with that hair?"

The actor has a point. In David O. Russell's disco era ensemble piece, loosely based on the late-'70s Abscam scandal and the ace scammer Melvin Weinberg, recruited by the FBI to take down money-hungry pols, it's hard at first to figure out how Bale's character pulls it off. With that hairpiece, that is.

(The sting operation is famously locally connected: Among the public servants convicted of accepting bribes were a New Jersey U.S. senator, two Pennsylvania and one New Jersey congressmen, a New Jersey state senator, and three members of Philadelphia City Council.)

In the film's opening scene, Bale's Irv is gingerly applying spirit gum, trying to stick a not-exactly-top-quality toupee to his head. When the camera pulls back, we see a guy of considerable girth. Bale, famous for shedding weight (60-plus pounds for The Machinist), gained 40-plus pounds to, er, embody Irv.

"When I first read the script by Eric Singer, which was a wonderful script, a historical drama," Bale says, "in my mind's eye I had pictured that Mel was probably a real smooth operator. Somebody very slick, very suave, giving the impression of being very moneyed, very erudite. And then when I saw a picture and I saw interviews with Mel, he was not any of those things.

"And I just found him mesmerizing and surprising and I said, 'OK, how did he, from the inside out, become that way?' . . . and from that moment I was just obsessed . . . I thought, I can't play this guy any other way. And especially with something like that comb-over. . . . I loved that contradiction."

Bale threw Russell for a loop, too, when the actor showed up for the first day of shooting with what cannot accurately be described as a beer belly - it's more like a whole brewery. But it works, gloriously.

American Hustle, which opened Friday and which looks - as did Russell's The Fighter and Silver Linings Playbook before it - destined for awards-season glory, is a story of epic flimflammery. With its original script overhauled by Russell ("a complete Page 1 rewrite," says Bale), American Hustle is a story of love, a story of reinvention, a story of graft and greed, a story of plunging necklines and polyester couture. Joining Bale in this craziness is his Fighter colleague Amy Adams, as a talented grifter Irv falls for (and vice versa), and Silver Linings lovebirds Bradley Cooper and Jennifer Lawrence, as an ambitious if not altogether sane G-man, and Irv's super-needy, super-coiffed spouse. Jeremy Renner, Robert De Niro, and Louis CK also appear.

In a way, every one of the characters is playing a con. And in another way, every one of the actors is playing his or her con - that's the nature of what they do for a living, right?

"Right," Bale agrees, with a caveat. "The difference being, obviously, that for the actor, the mark is in on it. The mark is a paying audience member, they are going along, they know - this is storytelling going on here. Hopefully there's no actual emptying out of people's savings accounts or anything like that."

(Well, there is that ticket price.)

"But in the sense that you have to believe it yourself in order for anybody else to believe it, yes, actors and con artists - they are completely similar," he adds. "The fact is that we're all giving a performance to some degree or another. Whether it be for the benefit of other people, or for our own benefit, it's a means for survival."

Bale, who won the best supporting actor Oscar in 2011 for his performance as crack-addled ex-welterweight champ Dicky Eklund in The Fighter, is famous for his total-immersion approach. He kept hours of recordings on his iPhone of his real-life American Hustle counterpart, Weinberg, playing them en route to the set, and between scenes, to nail the outer-borough cadences and crackling banter.

And, of course, Bale stopped going to the gym, and started eating - a lot.

His regimen? "I sat on my arse and ate doughnuts," says the Welsh born, L.A.-based actor, star of Christopher Nolan's brooding Batman/Dark Knight trilogy. Gaining weight, he reports, is far easier than losing it.

"It is incredibly easy for the first couple of weeks. No, I should say it's incredibly enjoyable for the first couple of weeks. Putting on weight is easy all the way through," he says.

"But after the first couple of weeks, the novelty wears off very quickly, and your body is groaning and starting to really shout at you, saying, 'Why? Why? Why? Why are you doing this?'

"So, it actually stopped being enjoyable much more quickly than I realized.

"But easy? Yes."