Should fat people be denied medical treatment because they have allowed themselves to become fat? The idea was first floated by the British Labour Party, and discussed in last week's NS by Richard Reeves, who wrote that the growth rate of obesity in Britain is now close to that in the US. I find this hard to believe. Yes, people are getting fatter in Britain - but, from my own completely unscientific survey, it is much, much worse here. And there is one indisputable fact: America is the most obese nation on earth.
It's getting worse, too: each year, about 300,000 Americans die prematurely because they are overweight; children, on average, are 20-30 per cent heavier than they were a decade ago and, as a result, type-two diabetes is increasing. All told, 120 million Americans are overweight or obese. For such people, hospital and outpatient care is 36 per cent higher than for those in the average weight range - and medicines cost 77 per cent more. Outside a middle-class belt where attitudes to food and drink are almost obsessively puritanical and people are the ideal weight, Americans are eating and drinking too much and getting too fat.
The plentifulness of food, and junk food in particular, is one obvious reason why. Young Latina women brought up on frugal but healthy diets in their home countries succumb to junk when they come here. The food industry spends $30bn a year advertising processed, fat-laden food - compared with the $10m a year spent by the government to push the virtues of fruit and vegetables. Eighty per cent of this food advertising is targeted at children, and the other 20 per cent at their mothers: no wonder McDonald's, one of the obvious offenders, is now introducing yoghurt and (sweetened) fruit as a sop to the health freaks.
But there has also been a change in the eating habits of Americans. Thirty years ago, Americans spent two hours on average preparing dinner each night; now it is just 15 minutes. Restaurants are offering ever-larger portions, which in turn makes people think they must do so at home: people now consume between 50 and 100 more calories at one sitting than they did 20 years ago. The Journal of the American Dietetic Association found that people now eat larger portions than in 1977 of 107 key foods, including bread, biscuits, cereal, chips, coffee, wine and fruit juice.
In a nation culinarily dominated by chips, crisps and burgers, the results have been devastating. Men older than 40 have increased their beer-drinking by one-third. Pot-bellies, which researchers have discovered contain dangerous "visceral" fat, predominate.
Why? Researchers blame, besides genetics, the frenetic lifestyle of the average 21st-century American, the abundance of junk convenience food, and advertising. Soon, the number of deaths from being overweight will overtake the number of tobacco-related deaths in this country; excess weight can cause heart disease, strokes and certain forms of cancer. Just 30 minutes of exercise per day, researchers say, can help offset these effects.
The city with the least desirable record in the country is San Antonio in Texas, which has the largest percentage of obese adults. Almost a third - 31.1 per cent of adults - are rated as obese; 65 per cent of the city's adults were considered simply overweight in a study in 2001, second only to Charleston, West Virginia - where 67.8 per cent are overweight.
In San Antonio, the people like their Tex-Mex food, and also their margaritas. They have an annual fiesta, an orgy of over-indulgence. And that phenomenon among Latina women is widespread in San Antonio: the health and weight of the large Hispanic population tends to deteriorate once they arrive in the US.
By contrast, the US city with the lowest obesity rate is Denver, at 14.2 per cent: no one is quite sure why, except possibly that the city tends to attract outdoor types who go in for more exercise. (This data comes from the Behavioural Risk Factor Surveillance System, which continually monitors health risk factors.)
But there is hope. Eighteen years ago, Dr William Dietz, a director of the Centres for Disease Control and Prevention, first conclusively linked obesity in youngsters to the amount of time they sat in front of television screens. Now, he says, "after three decades of frustration", he is finally being listened to.
And McDonald's, although still the country's most visited fast-food chain, is struggling, facing a decline in its share of the market. In the past five years, this has declined by 3 per cent - while Subway, which provides healthy sandwiches on fresh bread, has taken its place as the largest food chain in the US.
Perhaps the food and exercise fads of the middle class will yet trickle down to the mass of all the overweight Americans as the risks become better known. But, in contrast to the NHS, the American medical system is thriving more than ever on its fat and increasingly obese patients.