"Super Size Me" and "Fast Food Nation" are like the double-decker patties of a movie meal.

The Morgan Spurlock documentary shows what happens after the burger hits your growing gut while the fictional "Fast Food Nation" looks at the world behind the counter, where ranchers, meat packers (some illegals smuggled across the Mexican border), marketers, store managers and teen employees reside.

Richard Linklater, who directed "Fast Food Nation" and adapted the book with author Eric Schlosser, was a vegetarian long before he started this project, which took him and others inside a real slaughterhouse.

Asked in a phone interview how he gained permission to shoot there, Linklater says he told the operators "we were making a movie about the plight of Mexican undocumented workers who come North and work in the factories and their trials and tribulations. So I wasn't lying," since that is true, although the film goes beyond that.

"It was kind of like being an undercover investigative reporter or something. There was an element of that to the whole production, but you gotta do what you gotta do sometimes."

That includes delaying the bloody "kill floor" scene until late in the film for two reasons: Moviegoers aren't likely to bolt at that point, and they've come to care about the woman sent to work where cows are stunned, killed, sawed and skinned and internal organs removed.

"Fast Food Nation," opening today, revolves around a fictional chain called Mickey's. The book is a real-life examination of the industry, while the movie is an invented story that incorporates many of its elements.

The production shot in a restaurant during its off hours but designed menus, signs and specialities as if the crew were running a real eatery.

Although Mickey's sounds awfully close to McDonald's or Mickey D's, Linklater said the name passed legal muster because there are roughly 1,000 real restaurants called Mickey's and the movie treats McDonald's as a competitor.

Linklater, an Austin, Texas, filmmaker whose credits include "Dazed and Confused," "Before Sunrise," "School of Rock" and "A Scanner Darkly," had enjoyed Schlosser's book. But he didn't think about a movie until he met the author, who suggested a fictional take on it.

Schlosser and Linklater collaborated over a period of years while each was working on separate projects. "I'd been trying to get movies made about industrial workers and low-paid, minimum-wage workers" but never could get financing until now.

"I always had crappy, minimum-wage jobs; it's like my own background. I've always felt that viewpoint of our culture is completely unrepresented in our media landscape. It's almost like poor people don't exist. Struggling people, nothing is seen through their eyes."

Linklater thinks a more appropriate movie title might be "Fast Food, Slow Death Nation."

"From the corporate perspective, you have an entire population of 300 million strong, and they're really not thinking about their own health or their kids' health," the director says. The upper-middle or wealthy class, who think they deserve to be healthy, consider fast food to be an occasional family treat.

"It is the diet for poorer people," Linklater says, and they and their children pay the price with obesity, diabetes and other medical problems.

They have been "brainwashed" with a double whammy: to think they can't afford anything else and that they don't deserve to be healthy. It's the ultimate poor tax.

In the movie, Patricia Arquette plays a single mother who works at a pet store and whose brainy teenage daughter goes to school and runs the register at a Mickey's. The mom thinks all politicians are the same -- crooked -- and sees the proliferation of chain restaurants as a good diversion for her boring town.

"Patricia liked that character. She said she has friends kind of like that. ... Too damn busy between single parenting, making a living and keeping food on the table for your kid, you don't have any psychic space left," except for the occasional date.

Reading the source book reportedly changed the eating habits of many cast members, including Bobby Cannavale and Ashley Johnson. As for 46-year-old Linklater, he has been a vegetarian for more than 20 years.

"I was paranoid early about what they were feeding us," he said, but even he was shocked to see ground beef made.

"I thought I knew it all, but when I saw that, that it's actually the rejected pieces from all the real cuts, if it's not good enough to be a sirloin or a T-bone or whatever, and it all gets mixed in one big vat and there's a lot of fat added, these huge slabs of white stuff." It's worse than bologna or hot dogs, he says.

"I don't think I ever had that image in my mind. I still was under the delusion I had as a kid. 'Oh there's a farm and there's a cow, and they're raising the cow and I'm eating part of that cow when I eat this burger.' No, you're eating that cow and hundreds of pieces of other cows."

He quit eating hamburgers a while back. "I like veggie burgers. What I liked about the burger was the bun, the tomato, the ketchup, the whole way it feels in your hand. You can't even taste the meat. I don't think you really eat a burger for the meat, outside the delusion that you have to have meat to stay alive."

He is living proof that you don't.