Super Size Me was the most popular documentary of the year, and was nominated for an academy award. Its claims were generally accepted without critique by nearly everyone who watched it or even just heard about it. But this result was virtually guaranteed by Spurlock's choice of subject matter. McDonald's is probably the world's easiest target. It's always popular to be anticorporate; it's always popular to bash fast foods, and audiences are generally well predisposed to welcome any information that supports these concepts. ...One of my favorite podcasts, Skeptoid, had a fascinating episode recently, examining what "everybody knows" about fast food. Brian Dunning, who has impressed me mightily with his even-handed and scientific approach to every subject I've heard him cover, looks at the documentary Super Size Me versus actual scientific evidence. Luckily for us, he also puts a full transcript of his shows on his website so you can go read the whole thing if you don't want to listen. Check it out.
You see, Morgan Spurlock is not the only person to have ever tested fast-food-only diets, or even McDonald's-only diets. After his movie came out, many people repeated his experiment themselves, including a number of scientific institutions that applied controls and conducted the research in a scientific manner. At least three other documentary movies were made, Bowling for Morgan, Portion Size Me, and Me and Mickey D, in which the filmmakers lived exclusively on McDonald's food for 30 days but (unlike Spurlock) did not force themselves to overeat when they were not hungry. All filmmakers lost weight during the period and suffered no ill effects; and the subjects in Portion Size Me, which was scientifically controlled, also had improved cholesterol.