Earlier this year, the Centers for Disease Control and Prevention reported that the combination of "poor diet and physical inactivity" is now the No. 2 cause of death in the United States after smoking. "Obesity has risen at an epidemic rate during the past 20 years," says the CDC. It needs to be addressed in an urgent and thoughtful way.

But a new documentary called Super Size Me, which opened last week in St. Louis, does just the opposite. It is an outrageously dishonest and dangerous piece of self-promotion.

In the film, the director and star, Morgan Spurlock, eats only at McDonald's for 30 straight days while staying practically sedentary. He gains 24 pounds, his cholesterol rises 40 percent, he feels lousy and his sex life collapses.

Spurlock's antics send precisely the wrong message. He absolves himself and us of responsibility for our own fitness. We aren't to blame for being fat; big corporations are. And the remedy, he suggests, is to file lawsuits and plead with the Nanny State and the Food Police for protection.

Spurlock's weight gain and health decline have nothing to do with where he ate. It's simple metabolic math. Someone Spurlock's size can eat 2,500 to 3,000 calories per day and maintain his weight, say nutritionists. In the movie, Spurlock eats about twice that many calories.

There's no surprise here, except that gullible reviewers have embraced the movie and lauded Spurlock for his being oh-so-clever. He won best-director honors at the Sundance Film Festival, Roger Ebert and Richard Roeper gave the movie two thumbs up and reviews have been enthusiastic. Super Size Me could become one of the hottest movies of the season.

If that happens, Spurlock, a prankster and scamster from way back, will have the last laugh. It's no accident that he calls his production company The Con. Spurlock made his mark on American culture with a program he originally created for the Internet called "I Bet You Will," on which he paid people to do disgusting things. MTV gave it a brief run in 2002. In one stunt, a woman shaved her head, combined the clippings with butter to form a gigantic hairball and ate it. She got $250.

Spurlock is up to his old tricks in Super Size Me. This time, however, the person who cashes in is Spurlock himself.

The truth is, it is not easy to eat as many calories as Spurlock eats at McDonald's. Consider this daily diet: A breakfast of Egg McMuffin, orange juice and coffee; lunch of Big Mac, medium fries, Coke and hot caramel sundae; and dinner of 10 chicken McNuggets, sweet and sour sauce, milk and a Fruit 'n Yogurt Parfait total 2,730 calories, according to the McDonald's Web site.

Now, double all those quantities, and you get a notion of what Spurlock ate every day for a month.

Dawn Jackson of the American Dietetic Association notes that Spurlock ate the equivalent of 18 hamburgers a day. Couple overconsumption with nonexercise, and you gain weight and feel sick. It would be a miracle if you didn't.

The real question is whether you are you smart enough to see the true intentions of Spurlock and the agents of the Food Police in his film (like lawyer John Banzhaf, who sees a tobacco-like pot of gold in lawsuits against food companies). Jackson complains that the movie "gives the message that you can't eat healthy at a fast-food restaurant. That's not true."

It certainly isn't. She points out that a breakfast of Egg McMuffin and orange juice; lunch of Chicken McGrill sandwich, side salad, yogurt parfait and bottled water; and dinner of hamburger, small fries and Diet Coke all comes to less than 1,500 calories. Stick to such a diet, and a man Spurlock's size would lose a couple of pounds a week.

It's not where you eat. It's how much you eat and how much you burn off. What Americans need is balance: Sensible eating plus exercise. Staying fit is a matter of personal choice and responsibility, which are what this con man and his co-conspirators want to take away from you.

James K. Glassman is a resident fellow at the American Enterprise Institute.