Nota Bene: The standard spoiler disclaimers for any movie-related node apply, including those about spoilers. This being a factual documentary at heart, there aren't any plot points that can be spoiled by this writeup.
Super Size Me is Bowling for Columbine meets Fast Food Nation. It is an interesting, irreverent and at times shocking documentary about how McDonald's and other fast food restaurants are major contributors to the biggest public health issue of late in the U.S., obesity. The central theme of the movie is the month-long McDonald's-only diet, upon which its creator, Morgan Spurlock, embarks. After being pronounced a man of above average fitness by a personal trainer and being reassured of his excellent general health by three doctors at the start of the movie, Morgan gains 25 pounds, 60 cholesterol points and is subject to mood swings, chest pain and slight impotence a month later.
The rules of Morgan's diet were simple. He could only consume products available at a McDonald's "restaurant", including bottled water. Whereas he couldn't ask for super-sized portions, he would have to accept them, if offered by a McDonald's associate. Over the course of the documentary, he was offered super-size portions nine times.
Morgan's three doctors only foresaw a gain in blood cholesterol before he embarked upon his month-long diet. On day 21 of his diet, all three doctors suggested he discontinue the diet because his liver was turning into pate from the high-fat diet and his cardiovascular indicators were far from optimal. However, he persisted for nine more days and fulfilled his stated mission. By the end of his project, he had eaten as much fast food in a month as nutrionists recommend people eat in eight years.
The movie feels a lot like Michael Moore's documentary about America's guns -- informative and sometimes shocking commentary, accompanied with many interviews of common people, all centered around a main theme. Morgan Spurlock is originally from West Virginia, the 3rd most obese state in the U.S., just like Moore is from Michigan, a fairly gun-crazy state by his own description. There are some gross-out moments in the movie, such as when the camera focuses on Morgan's vomit after a heavy McDonald's meal. The film also includes some nice miscellaneous touches, such as appearances by his vegan-chef girlfriend and interviews, where most people off the street don't know what a calorie is. Repeated requests for an interview with the high-ups at McDonald's are refused. In general though, the film is a lot less abrasive than Bowling for Columbine, with Spurlock seeking to shove a lot less down the audience's throat compared to Moore.