John Wayne himself would be tempted to go vegan after watching Morgan Spurlock's ‘‘Super Size Me,’’ a documentary about one man's harrowing journey through an American wilderness of junk food and failing health.

The movie, which played to rapt audiences at the Sundance Film Festival last winter, is built around a now- legendary act of dietary masochism. Curious to see what effect it would have on his health and personal life, Spurlock — a New York-based playwright and video producer — would embark on a one-month McDonald's binge: No fruits, no vegetables, just McGriddles, Big Macs and Quarter Pounders three times a day.

If a Super Size was offered, he would accept it. Mimicking the lifestyle patterns of many sedentary Americans, Spurlock also would avoid exercise and limit his step count.

Spurlock, who is in excellent shape at the outset, expects the worst, and gets it. He gains 10 pounds in the first week alone. His cholesterol and blood pressure spike. He becomes irritable, headachy and lethargic and his sex drive plummets. None of this is scientific (Spurlock does hire several physicians and a dietary specialist to monitor his ‘‘progress’’) but it puts an amusing punctuation on the movie's central themes of epidemic obesity and sugar addiction.

When Spurlock marvels at the sheer girth of his first Super Size box of french fries — a half-pound of salty potato sticks — it's impossible not to share his giddy disgust.

Spurlock admits later that ‘‘Super Size Me’’ is a fait accompli, health-wise — restricted to an all-junk diet, who wouldn't expect to get fat and sick? Still, there are revelatory moments, particularly when Spurlock hits the road Michael Moore-style to shed light on the way the junk-food industry markets to children.

Visiting a middle-school cafeteria in Illinois, Spurlock reveals the sorry state of the nation's school lunch program, interviewing one girl whose midday meal was made up solely of three candy bars and a Coke. Other encounters are more innocuous, including a conversation with an apparently fit man whose lifelong love affair with the Big Mac compelled him to eat 741 of the suckers in 2002 alone.

Owing to the enormity of his prey, Spurlock's arguments seem unfocused at times, but what does come through clearly is alienation — a certain numbness created by the franchise culture. The most articulate mouthpiece of this idea turns out to be artist Ron English, whose distorted, nightmarish renderings of Ronald McDonald and other
corporate icons appear throughout the movie.

In an interview, English compares the strip-mall landscape to the never-ending background loop in a Flintstone's cartoon: Home Depot, Wendy's, Bed, Bath and Beyond, Home Depot, Wendy's and on and on. The implication is troubling and surreal: America is becoming a place where you can drive all day and never move an inch.
B+

‘Super Size Me’
Rating: Not rated (profanity, some nudity)
Running time: 96 minutes Playing: Opens Friday at Harkins Camelview in Scottsdale