NO-ONE ever knows what to expect with Richard Linklater. With his debut feature Slacker he helped define a generation of Americans. Waking Life and A Scanner Darkly overlaid liveaction photography with an advanced animation process called "rotoscoping" to pioneer a new form of story-telling. In between, Linklater directed Before Sunset and After Sunrise, a couple of romantic comedies shot in real time and involving the same characters and actors, but with a 10-year gap, and also the hilarious School of Rock and the baseball remake Bad New Bears.

Now he's filmed Fast Food Nation, Eric Schlosser's stomachchurning dissection of what goes into American hamburgers. But rather than deliver a populist Michael Moore-style documentary, the more obvious option, he draws on Schlosser's damning facts to create a fictional story about workers caught up in the meat trade's dubious practices.

"I'm trying to pull back the curtain and see what they don't want to show you, " he says. "I thought by concentrating on the stories of the workers in the food chain we could do what cinema does best. It makes you identify for better or worse with whoever is up there on the screen. My goal was to put people up there . . .

people who are demonised in our culture, like the illegal Mexican immigrants working in the slaughter-house, or just ignored, like the waitress selling hamburgers, and share their experiences."

Fast Food Nation hasn't been made as a political film, but it has a political sense to it. "Genre entertainment has always been a way to smuggle ideas and parallels and subtexts, " says Linklater.

Greg Kinnear is brilliantly cast as a marketing director dispatched to Colorado by his company to investigate claims that the meat supply for their Mickey's Big One hamburgers has been contaminated by animal excrement. Yet when he discovers how illegal immigrants are exploited and animals are tortured in order to produce cheap food for America's shopping malls, a plant manager . . . played by Bruce Willis . . . shrugs it off, saying: "The truth is we all have to eat a little shit sometimes."

Shocked though Kinnear is, don't expect him to rock the boat or do anything rash that might threaten his comfortable desk job back in the corporate HQ.

"That's what's scary about the human psyche, " says Linklater.

"We all have an incredible ability to assimilate things and rationalise them, and say, well okay, that's just the way it is, it's always been that way. You have to remember that people worked in concentration camps and went home to their families every night."

Born in Houston, Texas in 1961, Linklater quit college in 1982 to work on an oil rig in the Gulf of Mexico and earn enough to pay the bills while he tried to become a film-maker. He moved to the state capital Austin, an easygoing college town with great music and a spirit of independence, where he became a director just by going to films . . .

he got inspiration from Ophuls's La Ronde and Bunuel's The Discreet Charm of the Bourgeoisie . . .

and making shorts as technical exercises, rather than going to film school. "I didn't have to answer to anyone. I didn't have to get grades. I learned to trust and cultivate my own instincts."

Just as Austin confounds the stereotypical image of Texas as being a place of men wearing 10gallon hats and of women who are all lip-glossed Sue Ellen clones, Linklater fails to fit the common description of an independent film-maker. "Early on people were trying to categorise me, but in the arts of all places there should be no categories. I guess if you do anything long enough you earn a latitude to be yourself and be able to follow your own human interests and make films about them. I haven't had maybe enough success to solidify me into a speciality. I think if you make an action thriller and it's really successful, that's what you're going to do because the rewards are there. But I haven't been rewarded. I think I have a pretty low threshold of what I think a movie can be. To me, it can be just two people in a room.

I see movies as sketches, maybe, instead of big canvases. Fast Food Nation is a kind of hybrid. It's a super low-budget seat-of-thepants kind of operation and yet it has a pretty large epic structure."

So epic that within a series of seemingly simple overlapping stories a picture emerges of corporate moral meltdown. "The American corporate structure allows you not to be human, " he says. "It's sort of running itself, it's so vast. It's an efficient profitable model that satisfies on some levels, but it's really overreached itself and is an active agent for evil on so many other levels. We've got to rein it back in."

Linklater's eyes were opened by what he saw while he was shooting Fast Food Nation. "All the rejected meat that didn't qualify to be a cut, it's all stirred up. The white stuff is fat that they put in. The red stuff is all the hearts."

Although he's become a vegetarian, he's not against meat.

"You can still eat burgers, " he says. "You just don't have to eat that kind of burger. You can find a place that does it with organic meat that isn't hormone and antibiotic injected and that didn't lead an awful life in a feed lot. You just have to know about it and put your consumer dollars there.

People should get closer to their food supply. They should go to farmers' markets and buy food that was grown just up the road or outside the town.

"If kids have never had healthy food, it doesn't taste very good to them. So it's hard to compete with burgers and French fries.

Basically these kids are addicted.

It's like being addicted to cigarettes or alcohol or drugs. I'd be happy if fast food went the way of smoking. I certainly don't want my three daughters eating it, at least until they're 16 and can make the choice for themselves."

Fast Food Nation is produced by Jeremy Thomas with the backing of Participant Production, the company set up three years ago by eBay billionaire Jeff Skoll to produce dramas rooted in challenging contemporary issues.

Its first slate of releases included Good Night, And Good Luck, Syriana, North Country and Al Gore's An Inconvenient Truth.

Gore turned to cinema because the discourse of democracy has been reduced to soundbites. "If you raise your voice you're either unpatriotic or you're an elitist, " says Linklater. "What Gore provided for himself . . . was a forum to speak uninterrupted and to get his global warming argument across directly instead of in soundbites saying this is the science, only to have someone else say no this is the science, with the TV interviewer then concluding blandly, there you have it, two sides, so I guess it's all undecided. The more something matters in the US, as Noam Chomsky has pointed out, the less it can be discussed."

Linklater is not sure what he'll film next, but he's not pessimistic. He's always managed to make the movies he wants. "You're in the system but you're trying to make it work for you as much as you're trying to work for it. You're trying to subvert it and tell your own story and do whatever you can within it. Subversion is just showing the other side of something that's true but hidden. It's just showing something real. Hollywood has never been a moral entity. If they think people will watch these movies, they'll keep making them."

'Fast Food Nation' opens next Friday