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Finally, somebody’s thinking of the children. In Super Size Me, a critical look at our ever-expanding fast-food nation, filmmaker Morgan Spurlock learns that, in a culture in which little ones are more likely to recognize Ronald McDonald than Jesus, bad habits begin early. Advertisers, lazy parents, and even poor urban planners all have a hand in creating children’s positive associations with cheeseburgers and fries—greasy treats served in restaurants where toys and playgrounds take the place of Brussels sprouts and polite dinner conversation.

This pervasive good-time feelin’, Spurlock suggests, is an obvious contributor to America’s obesity problem. So when talking to a nutrition expert about teaching the young to make healthy choices, he graciously shares his plan to protect his progeny from burger chains’ seductive forces: “That’s why, when I have kids, every time I drive by a fast-food restaurant, I’m gonna punch them in the face!”

It’s that silly yet informed approach—not to mention some especially brisk storytelling—that makes this our-nation-at-risk documentary such sickening fun. Inspired by the 2002 lawsuit filed against McDonald’s by two overweight teenage girls, the 33-year-old Spurlock decided to find out what would happen if he lived “every 8-year-old’s dream” and dined nowhere but at the Golden Arches for 30 days. He would stick to three rules: ingesting no food, including water, that didn’t come from behind the counter; eating every item on the menu at least once; and supersizing only when offered.

Before delving into his personal odyssey, Spurlock lays the groundwork with a quote from McDonald’s Corp. founder Ray Kroc: “Look after the customer and the business will take care of itself.” Then he unleashes a deluge of stats: One in four Americans eats fast food every day; 60 percent of us are either overweight or obese; obesity is approaching smoking as the leading cause of preventable death in America; McDonald’s feeds more than 46 million people daily, which is more than the population of Spain. As Spurlock rattles off the numbers, his camera shows what our malnourished eyes probably barely notice anymore—that McDonald’s, Wendy’s, and Burger King joints are everywhere. Even, horrifyingly, in hospitals.

Similar revelations come throughout Super Size Me, including those involving Spurlock’s experiment, which he approaches with a scientist’s attention to detail. The filmmaker secures the services of three New York–area doctors—a cardiologist, a gastroenterologist, and a general practitioner—along with a nutritionist and trainer from a wellness center. He gets a pre-diet examination from all of them, then continues to check in throughout the 30 days, keeping logs of his meals and a mental checklist of his ailments.

“Mental,” in fact, is the word that occasionally pops into mind while witnessing Spurlock’s saga. There’s no question that eating a month’s worth of Filet-O-Fishes and fries would leave even the steeliest stomach a mite queasy, but some of Spurlock’s reactions are a bit hard to swallow. His first supersize challenge, for example, comes within the first week of the experiment: a double Quarter Pounder, a gigundous Coke, and fries that are “like 4 feet tall.” After he downs the meal, his jokey enthusiasm soon devolves into a humorous list of symptoms: “McGurgles,” then “McStomachache,” then “McGas.” Then Spurlock leans back into his driver’s seat with a sigh and a “just give me a minute.” Then he vomits.

Seems like it would take more than a single supersized meal to make a healthy 33-year-old vomit, doesn’t it? Other complaints are similarly head-scratching: One doctor responds to Spurlock’s testament of a “freaky feeling in the groin area” with “That is odd”—though Spurlock’s horrified but game girlfriend, a vegan chef, at one point daintily comments that she believes “the saturated fats are impeding the blood flow to his penis.” Another doctor later tells him, “I don’t have a ready explanation for your chest pain.” Nonetheless, no one’s surprised when Spurlock’s numbers—weight, cholesterol, liver capacity—take an immediate and serious turn into red-alert territory; one physician even compares the project to Nic Cage’s suicidal drinking in Leaving Las Vegas.

But even when his health takes a turn for the worse, Spurlock keeps his sense of humor. Near the end of the film, his girlfriend asks him why he would continue to eat meat after this, when he knows that the system is “immoral and wrong and hurtful.” To which Spurlock replies that he simply likes burgers and steaks and pork chops, thank you very much, and hints that she needs to relax: “Ham is the greatest thing ever! Heroin and ham are not in the same categories!”

Spurlock’s lighthearted tone, however, never dulls his sharp reporting, which goes beyond investigating the fast-food industry to studying school-lunch programs (most of which are unpardonable), the addictive qualities of a lot of junk food (“If you’re a 12-year-old kid, your brain is no match”), and Americans’ tendency to seek quick fixes such as gastric-bypass surgery instead of devoting time and money to longer-term approaches to overall health. To his credit, Spurlock tries to balance his easy-target polemic with musings about personal responsibility: Throughout Super Size Me! he keeps returning to the idea that the proliferation of cars, takeout, and advertising is no excuse for a society that’s effectively killing itself.

It’s an awareness that was clearly lacking in the lawsuit that raised the director’s ire in the first place, one that is eventually—relievedly—expressed by one of Spurlock’s off-the-street subjects: “We can go into McDonald’s and grab a salad,” the unidentified woman says, “but we choose not to.”CP