“Patient is embarking on one-month McDonald’s binge”, writes pragmatic GP Daryl Isaacs in his medical record for a fighting-fit Morgan Spurlock. The young American filmmaker has decided that he is going to eat nothing but McDonald’s food, for three meals of every day for a whole month. He will try everything on the menu, and if asked to “super size”, he will accept the challenge.

It seems this intriguing n-of-1 trial, documented on film in the tragi-comic Super size me, was the brainchild of a creative man. Or maybe it was a “gut response” to the judgment handed down in failed US legal action against fast food giant McDonald’s. The legal team for the plaintiffs (two very overweight teenagers) had failed to establish that McDonald’s should be liable for their clients’ obesity, in part because we all know (don’t we?) that fast food may be harmful and that it isn’t meant to be eaten for three meals a day.

At the start of Spurlock’s McTrial, his GP and other professional advisers — a gastroenterologist, a cardiologist, a dietitian and an exercise physiologist — were expecting to see relatively minor changes as a result of his “Mac attack”, among them a rise in serum lipid levels and an increase in weight. None of the team seemed particularly worried. But fairly early on they start advising him to stop, or at least modify, what he is doing. A little later they are trying to convince him, in no uncertain terms, to stop the experiment altogether. His dietitian worried about weight gain and poor nutrition; the doctors were concerned about his rising liver enzyme levels; and his mother offered him a portion of her liver should he need a transplant! His girlfriend Alex — who just happens to be a vegan chef — stood by her man despite her fears for his health. Everyone can see where Spurlock is heading, and the trial doesn’t end a moment too soon for this young man’s peace of mind.

Throughout, Morgan’s ever-present, ironic humour keeps the viewer entertained and engaged — for example, after his baseline physical, which included a per-rectal examination, he quipped: “I like my doctor to be thorough”, and after his first super size meal he reports symptoms of “McGas”, “McSweats” and McTwitches”, as well as “feeling a little McCrazy”.

The film travels well beyond the filmmaker’s personal experiences. Although McDonald’s has received special attention in the film because, as one interviewee said, it “lures in young children”, Spurlock also takes us to schools, professorial offices and boardrooms around America, showing us how fast foods in general and their supporters have conquered not only neighbourhoods but also school canteens and government legislators. Former US Surgeon General David Satcher and Professor Kelly Brownell, Director of the Yale Center for Weight and Eating Disorders, are among the many experts interviewed. Spurlock’s film explains how fast food can conquer us as individuals (and whole nations?), with its cocktails of addictive constituents and why it has a starring role in the current epidemic of obesity and obesity-related diseases.

It is no surprise that this documentary is already winning major awards, including for Best Director at this year’s Sundance Film Festival. Super size me exhibits a wonderful balance: as funny as it is informative, as intimate and personal as it is professional, and as affectionate about McDonald’s as it is castigating. If only all fast food was as balanced nutritionally.