Richard Linklater may be the most versatile and nervy American filmmaker working right now, successfully hopscotching between broad, yet culturally aware, comedies (“School of Rock”) and visionary hybrids (the live-action animations of “Waking Life” and “A Scanner Darkly”). An adaptation of Eric Schlosser’s 2001 behind-the-griddle exposé “Fast Food Nation” might have seemed a shoo-in given the satirical potential inherent in our national schizophrenia over the happy meal crisis: We crave that double-meat-and-cheese, but please hold the trans fats or we’ll sue. Our girlish figure, after all.

Inevitably, Mr. Linklater’s collaboration with Mr. Schlosser on a fictional version of the book proves misguided. As a creative strategy, it makes sense: Producing a documentary about the perils of the fast-food industry may seem redundant after Morgan Spurlock’s absurdist “Super Size Me.” Yet this long-winded treatment plays out with a clunky, multilayered story that jostles uneasily between satire that isn’t quite funny enough, righteous speechifying that rings canned rather than fresh, and social drama that feels as prefabricated as those all-beef patties that oppress our souls.

It’s a shame, too, since Greg Kinnear offers such comedic promise as a rising corporate strategist who is the mastermind of “The Big One,” the whopping new burger sold by Mickey’s — a regional chain that, as its name implies, competes like a second-rate version of McDonald’s. As the movie opens, Mr. Kinnear’s Don Anderson learns that the meat his company purchases cheaply from a Colorado plant is tainted with dangerously high levels of E. coli bacteria. Or, as his boss tells him: “There’s s— in the meat.”

The movie makes sure to recycle variations on that line several times, playing for laughs or shudders. The crisp, quizzical Anderson ventures to a small town in the Rockies that is gradually turning into one of those sprawling exurban communities, licensed to root out the corrupt Mickey’s middleman responsible for the poor test results.

Meanwhile, in a parallel story, a group of Mexicans have crossed the border illegally in the back of a coyote’s van and camped out at a cheap motel not far from the processing plant. Several of them, including Raul (Wilmer Valderrama), take jobs at the plant, risking life and limb in hazardous conditions as they hose down and chop up slaughtered cows. There’s a vile, racist plant manager who barks at the men as if they were the cattle and reserves a different sort of treatment for the women, whom he freely molests and introduces to the joys of methamphetamine. Raul, who, with his extraordinarily compassionate sweetheart, Sylvia (Catalina Sandino Moreno of “Maria Full of Grace”), appears set on a course that will end in tragedy, is still recognizably the Mr. Valderrama we know from “That ’70s Show.” And though he never quite ends up fed to the meat grinder, there’s a part inside every viewer that will silently hope he does, if only because the soulful, suffering earnestness of the film’s Spanish-language segments fail to mesh convincingly with the winking flippancy of the scenes featuring Mr. Kinnear.

There are maybe a dozen casting surprises in “Fast Food Nation,” which is stuffed with notable faces making brief appearances and dispensing quirky philosophical asides. There’s an additional plot involving a hard-working high school student (Ashley Johnson) who struggles with the morality of running the cash register at a Mickey’s franchise and becomes involved with a feckless gang of pimple-faced ecological activists, as well as fleeting cameos from the likes of Bruce Willis (brilliant as the defiant executive who schools Mr. Kinnear’s would-be whistleblower) and Kris Kristofferson (as a grizzled cattle baron griping about the decline of the American way of life). It’s almost the same role Mr. Kristofferson played in John Sayles’s “Silver City,” skewed to Democratic affinities, and it prompts the notion that “Fast Food Nation” may be Mr. Linklater’s unwitting answer to Mr. Sayles’s actorly message movies. (Or, perhaps, this is what Mr. Linklater’s “Slacker” would look like if it was directed by Mr. Sayles).

The problem is, of course, that while the movie is as stuffed with engaging and thoughtful asides as a bulging sack of White Castle burgers, it is as similarly packed with empty calories. Rather than let Mr. Kinnear carry the narrative, which would have compelled an incisive focus, Mr. Linklater cuts his point man loose halfway through, then radically shifts the tone of his film at the very end. It doesn’t sit well in the stomach, which may be part of the point, but neither does it fully digest as satire or op-ed broadside.