Fatland is an exhaustively researched, and occasionally exhausting, treatment of the science and culture of fat. Although it can be hard going in places where the essential but dull biochemical detail can threaten to sink the book, there's more than enough meat to sink your teeth into if you stick with it. It's never less than readable. Unlike most books on weight matters, Fatland blames and accuses further than the fast food industry, and it's about time. It explains what made Americans the fattest people in the world (apart from a few South Sea islanders), why their continent is facing an epidemic of fat-related illnesses - such as adult diabetes at ever-younger ages - and what pushed one scientist, James O. Hill, to make the widely-repeated claim that almost every American will be fat by 2050. By the end, you'll be an expert on fat, and much, much more likely to cut the grease from your diet than you were after you finished Fast Food Nation.

Greg Critser, who used to be blasé about his weight himself until someone screamed abuse at him and he had a moment of clarity, takes the subject of fat and splits it up into sections. The first, "Where the calories came from", analyses how under the watch of Earl Butz, Richard Nixon's agriculture secretary, High Fructose Corn Syrup (HFCS) and Palm Oil transformed the food industry in the 1970s. HFCS keeps food tasting good and prevents freezer burn, and palm oil was sold to the American housewife as a fat as healthy as olive or sunflower oil. In fact, palm oil is more chemically similar to beef tallow, and HFCS is not digested like other sugars. In a later section, "What the calories do to you", Critser explains that HFCS bypasses the normal breakdown process and arrives intact in the liver, "skewing the body towards fat storage" and later, diabetes. It's use is so universal that, as the author points out, "Soda is, 99 out of 100 times, nothing but HFCS and carbonated water, with a few flavouring agents thrown in for brand distinction".

In the second chapter, "Who got the fat into our bodies", Critser covers "supersizing", how the fast food industry made more profit by offering larger and larger size meals for minimal extra cost and convincing consumers they were getting great value. He details how fast food has carved out a presence for itself in the nation's schools and how McDonalds publishes a nutrition guide that teaches kids with diabetes how to calculate their diabetic points. This has been done to death before, but what hasn't, and what is far more interesting, is his analysis of the cultural tolerance and acceptance of obesity. He discusses how restaurants introduced bigger chairs for fatter clients, how religion condoned "gluttony" amongst its flocks as it concentrated on other sins such as sexual promiscuity and alcoholism, and how clothing retailers introduced jeans that came in regular fit, easy fit, loose fit, and baggy fit - "in reality simply bigger sizes, without the bigger numbers".

He also condemns the flood of diet guides and fads, such as Protein Power, The T-Factor Diet, and the currently popular Atkins Diet, which was sold with the promise that "you can burn more fat watching TV than exercising". As Critser observes: "The very notion of self-control was anathema to the new generation of diet books". The false and misleading claims made by these books, which were invariably bestsellers, were compounded by the advice dished out by American exercise councils. A mixture of political correctness and Republican cutbacks on funds for physical education combined to limit the US population's access to and understanding of the necessity of exercise. Particularly damaging to the nation's health was the indulgence shown to them by the experts. Doctors said that "doing a few minutes of housework" could substitute quite nicely for more vigorous exercise. Dr C Wayne Callaway, of the Dietary Guidelines Committee, refused to sign off on the statement that: "One thing is definite. To lose weight, you must take in fewer calories than you burn". He viewed it as "authoritarian".

Critser also attacks the self-appointed gurus, such as the holistic nutritionists Harvey and Marilyn Diamond, who advised parents to give in to all their children's demands at the dinner table. He believes the spread of loose discipline, which he ascribes partly to political correctness and partly to the American tradition of the child as the family's "very reason for being", will do long term damage to the nation's perception of food. "As a result", he says, "the American child commands disproportionate 'respect' - he isn't to be hurried too quickly into the pain of adulthood. Rather, he is to be mollified with the tremendous bounty of the new nation. And the nation's greatest bounty is food, glorious food". If this doesn't change, he stresses, James O. Hill's prediction will almost certainly come true.

This book is a revelation. It is the frankest and least hysterical treatment I have seen of obesity, and unlike other authors on nutrition Critser doesn't shrink back and rein himself in when he thinks he might be saying something unpalatable. And he pulls it off. He's blunt without being insensitive. He tackles fat head on. And he's not even pessimistic. He believes America really can turn itself around, just like he did. All it needs is a moment of clarity.