This film is to McDonald’s and fast food what Michael Moore is to George W. Bush.

There have been many other films about food, mostly negative. In Marco Ferreri’s La Grande Bouffe, Marcello Mastroianni and some others set out to kill themselves in an orgy of food and sex. Monty Python’s The Meaning of Life has gourmand Mr Creosole eating until he explodes all over the restaurant.

Then there are the maggots in the sailors’ meat in The Battleship Potemkin and the magnificent banquet served to the sad old-timers in Babette’s Feast.

Morgan Spurlock, a New York-based filmmaker and playwright, sets out, in this his first feature-length film, to address the problems posed by the worldwide expansion (that’s the right word) of fast-food chains and the rise in obesity.

He turns himself into a guinea pig for a month by eating three super-size meals a day bought at McDonald’s and nothing else, and is continually examined by an army of doctors and nutritionists in the process.

Following the film’s appearance (it won the Best Director award at the Sundance Film Festival last year and The Guardian’s New Director Award at the Edinburgh International Film Festival) McDonald’s have now cancelled their super size policy, though they deny it is a result of this film, and have launched a counter-attack by coming out with ‘healthy’ options. They have also taken out ads congratulating Spurlock, presumably through clenched teeth, on how entertaining he has been.

The counter-arguments are plain: isn’t it obvious one is not supposed to eat at McDonald’s all the time? And if one eats nothing but organic apples all the time, wouldn’t that be bad as well?

More than just about McDonald’s, the film is about obesity and the self-abuse – for that is the right word – that leads to it. It is also a comment on the commercial pressures that invade the schools and the imagination of children, which is a prime contributor to the obesity one sees so much around.