Politically incorrect or not, there was only one description fitting the man tucking into a meal outside one of my local fast food outlets: fat.

 His body oozed over the edges of his chair in the same way as his burger and the lot were oozing over the bun, dripping tomato sauce on to his bucket of chips. Later, when he walked past us, I could clearly hear his laboured breathing. "A heart attack waiting to happen," my friend whispered. This man's health should be none of our business. Neither should his appearance or his eating habits. He's a grown-up. It's a choice he makes. But, increasingly, obesity and the accompanying health risks are becoming a major financial as well as health issue in Western countries.

 In the US, for example, it has been estimated that the cost of obesity-related illness and ailments is $A204 billion a year. In Australia about 60 per cent of adults are either overweight or obese, and a recent report says half of Australian children will be overweight or obese by 2020.

 So it was inevitable that fat would become food for lawyers, in fact potentially a multi-course legal banquet.

 According to Professor John Banzhaf, a lawyer and teacher at George Washington University in the US, suing fast food companies may be one solution to the society's ever-expanding obesity problem.

 Don't laugh. They laughed 30 years ago when Banzhaf first mooted the possibility of smokers suing tobacco companies for compensation.

 Banzhaf, who runs a highly popular course on legal activism, acknowledges there are important differences between the problems from smoking and obesity.

 For example, tobacco is addictive; foods are not harmful when used in moderation, whereas cigarettes are; the link between lung cancer and smoking can be shown, a link between obesity and, say, heart attack death may be far more tenuous.

 Then there is the issue of how you prove which fast food chain, as well as numerous other sources of high-fat, high-calorie foods, should be held responsible for personal obesity.

 While all this sounds like yet a further erosion of the concept of individual responsibility, Banzhaf argues that legal moves against the fast food companies reinforce the principle.

 "Some argue that there is a right to voluntarily engage in unhealthy behavior, but there is no right to require others to subsidise the huge costs," he says.

 "The principle of individual responsibility arguably requires people to bear the consequences and the full costs of their own choices, and higher health insurance costs for those who live unhealthy lifestyles, as well as taxes on unhealthy products, are two ways to move towards this goal."

 Banzhaf sees a sliding scale of action, primarily targeting the type of information presented to consumers about food.

 For example, he predicts class actions against companies who do not clearly indicate the fat content of their product. Companies who put out "energy food bars" or "health bars" will be targeted to prove that's what they really are.

 There already have been successes. Earlier this year McDonald's was forced to pay $US10 million to a group of Hindu and vegetarian charities as part of the settlement for cooking its french fries in the less healthy beef fat rather than vegetable oil.

 Where the US leads, Australia usually follows, and "fat fraud" is already on the legal radarscope.

 Dr Simon Longstaff of the St James Ethics Centre says the fast food industry spends a lot of money trying to influence people, and with that influence comes responsibility. The manufacturers need to have a long look at their target audience and see if they are in a position to be able to make an informed decision.

 "It works both sides of the street; consumers should exercise more caution but manufacturers should weigh up the risks," he says. "But if consumers are to make those decisions, it needs to be an informed choice."

 During the early days of the campaign against cigarette companies, Banzhaf had a small rubber stamp on his desk proclaiming "Sue the bastards".

 The problem today is that as our dominant philosophy becomes to seek recourse through formal legal channels rather than exercising good judgment in the first place, the list of potential bastards seems to get longer and longer. And the people likely to get fat on this issue will be the lawyers.