It’s one thing to say that diet has a lot to do with the growing obesity problem in America, quite another to prove in court that client A’s heart attack was caused specifically by McDonald’s hamburgers, or by excessive bingeing on Cherry Coke. Nobody sticks to one brand of food like they stick to one brand of cigarettes, so individual suits are out of the question and class action suits would have to depend on highly complicated statistical analyses of food intake and medical cause and effect. Also, unlike smoking, there is nothing intrinsically unhealthy about eating. From the standpoint of food chemistry, at any rate, the worst that can be said about junk food is that it contains large amounts of sugar and fat, both of which are actually important parts of a balanced diet as long as they are consumed in moderation. Can individual food companies really be held responsible for the immoderate appetites of their customers? Clearly, if there is a legal case to be made, it is going to have to be fairly ingenious.Banzhaf’s approach is a gradualist one, to start with the relatively easy stuff and see how far he can take it.

The first line of attack is to go after food companies that misrepresent their products by understating the fat content, say, or omitting to mention certain ingredients. That is the basis of all the suits currently going through the courts. The second, slightly harder one is to accuse companies of making misleading health claims for their products – proclaiming pork to be “the other white meat”, for example, when its fat and cholesterol content are in fact closer to beef than to chicken.The third approach would be to pick up on sins of omission, or failure to warn consumers of certain health risks. Is it wrong of a fast-food chain to fail to point out that its triple-bacon double cheeseburger supersize meal contains more fat than any sane human being should consume in a week? Arguably so. Is it grounds for a lawsuit? Maybe, if the plaintiffs can work with laws on “clear and conspicuous disclosure of material facts”.And finally, the real zinger, if it can be made to work: an onslaught on the junk-food industry as a whole, in which McDonald’s et al would be made to pay their share of responsibility for the adult-onset diabetes, sclerotic arteries, heart attacks and strokes that fast food helps to cause.

Legal analysts are highly sceptical as to whether such an approach could ever work, and even Professor Banzhaf describes it as “a reach”. But there are some promising avenues to explore, including the possibility of describing fast food as something akin to an addiction deliberately fostered by manufacturers through their marketing, especially to children.”We know that people can become biologically predisposed to getting overfed, that once they grow extra fat cells, their bodies become accustomed to having that fat,” he said. “Those fat cells never die, and even if you lose weight they lie dormant and constantly try to get you to eat more. It’s not an addiction exactly, but it doesn’t leave people with a completely free choice in what they eat, either.”Banzhaf has other strategies up his sleeve, first developed in the tobacco campaigns, for exerting pressure on government. One is to push for higher health- insurance premiums for the overweight, a measure that would act as an incentive for people to shed some pounds, and would also shift more of the health-care costs towards the people who incur them Another is to push for higher taxes.