The Texan town of San Antonio is sometimes described, a trifle optimistically, as America's answer to Venice. Instead of gondolas, there are magenta-coloured barges which transport tourists along a two-mile stretch of river, past the native cypresses and gaudy glass-fronted hotels.
This is a town where you can really eat. The choice of cafés lining the riverside is dazzling: Tex-Mex, Chinese, Italian, Spanish and Indian all vie to outdo each other on price and size. Steaming platters of enchiladas are carried out to customers. The chips seem to last forever. Pepsis and Sprites come in a 'double-gulp', bucket-sized cone.
Lodged in the arid plains of southern Texas, this colourful town is best known as the home of the Alamo, the fort defended by Davy Crockett and Jim Bowie against the Mexicans.
Now a more dubious distinction has put it on the world map. Last year, it was named as the fat capital of the States. This title extends to the globe, as the US has the highest international rates of obesity. Just over 31 per cent of its citizens are obese, meaning that they have a body mass index of 30 or more. For a 6ft man, that equates to weighing 16 stone or more. A 5ft 6in woman would have to be more than 13 stone to qualify. The survey of risk factors compiled by the federal Centers for Disease Control and Prevention found that more than two thirds of the district's population is overweight.
Stroll downtown and the statistics become very real - and very open. Women who would put a strain on any set of bathroom scales wear shorts and T-shirts, not the long skirts or leggings which are used to shroud the flesh in Britain.
More than one million people live in and around Fat City, as San Antonio is known. Many are poor, a state which is linked to a sugar and fat-rich diet. Poor mothers tend to have underweight babies who through their lack of nutrition in the womb become biologically programmed to store fat super-efficiently in their youth. Around 40 per cent of the population is of Hispanic and South American extraction, and they appear genetically prone to being overweight.
In San Antonio, it is almost impossible to walk anywhere as the blocks are so large, the roads so wide. The only people you see using their legs are tourists or the homeless.
But, as in Britain, the major cause of adult obesity can be traced to schools. A breakdown of the daily lives of San Antonio's youngsters provides grim reading for those concerned about Britain's growing obesity crisis. Most children are bussed in or driven to school. They have school lunches provided by Pizza Hut and other companies which have an enormous commercial interest in trapping a new generation.
Belatedly the politicians have woken up to the scale of the epidemic - but they are finding it almost impossible to act. A first easy step might be to take fizzy drinks out of school corridors, but even that is beyond them. In Texas, the food giants put $54 million a year in to schools to sell their wares in vending machines, and that money goes directly into buying books and computers. The only action officials can take is to insist that healthier drinks are also sold in the machines.
Dietary lessons are carried into adulthood. In April, the town comes alive with a 10-day festival, where every street is filled with stalls selling tacos, sweetcorn, enchiladas, chilli hot dogs and cakes.
But it is not the annual fiesta which is to blame for San Antonio's crisis - it is a whole way of life. The food is plentiful and cheap. In the local Steak Escape, for example, a meal of a seven-inch steak, chips and coke costs just $6.09 (£3.78). A chilli-cheese hot dog in the A&W All American food bar, containing more than 700 calories, is $2.79 (£1.73).
American experts came to Britain last week to warn about the dangers of 'supersizing', the marketing of bigger portions of fatty snacks to ensnare consumers. Dr Jeff Prince used a distinctly unscientific term, 'humungous', to describe the size of the portions which American snacks have reached. A chocolate chip cookie, he revealed, is 700 per cent bigger than in 1982.
If it all begins in school, it ends in the clinic of the local bariatric surgeon, who for several thousand dollars will perform a gastric bypass operation which ensures rapid weight loss for at least three months.
When patients become morbidly obese, carrying around 100 excess pounds, they are eligible to receive surgery under their health insurance. By that stage, they will be suffering from related conditions such as diabetes and heart problems, and surgery is their only chance of avoiding a premature death.
Down at the town's Santa Rosa medical centre, Dana Reiss, one of the town's four bariatric surgeons, said: 'These patients are desperate. Many will have been on diets for most of their adult life, but they never work. This surgery is a last resort, but it does force patients to change how they eat.'
Many patients are not eating out of hunger, but out of habit and because they cannot face other problems in their lives. 'This is a disease of plentifulness,' said surgeon Paul Selinkoff. 'There's so much opportunity to eat all the time.'
Alexandra Tavassos, 36, does not know how she became so fat - large enough not to fit in restaurant seats or wear a seatbelt in the car. Last year she had the surgery, and lost 96 pounds. Now she is struggling to understand why people treat her differently. 'I'm an architect,' she explained. 'I've done the same job for years, but I've begun to notice that colleagues stop and chat to me. These are people who used to pass by my desk. Did I really seem so different to them when I was fatter?' The answer has to be yes.
Big in America
58 per cent of Americans are overweight, and almost 21 per cent obese. The rate of obesity has more than doubled in the past 18 years.
The size of portions has soared. The average muffin is 333 per cent larger than it was 20 years ago.
One in five American children is overweight.
Americans who live in sprawling towns where the car is the only reliable form of transport are up to six pounds heavier than those who live in cities.
