Two in three Americans classed as overweight

American waistlines are ballooning, with more than 30 per cent of the population officially defined as obese, according to figures published yesterday.

The epidemic of obesity, up a third on a decade ago, affects all ages, sexes and races and shows no sign of slowing, researchers from the National Centre for Health Statistics said.

President George Bush demonstrated the alarm at the growing threat last summer by instructing Tommy Thompson, his Health Secretary, to take public walks to get the nation moving. The chubby Mr Thompson declared earlier this year that he would have to lose 15lb (7kg) because he was overweight.

But confirmation that public health efforts to persuade Americans to tighten their belts have failed came from the latest National Health and Nutrition Examination Survey, which has been run regularly since 1960.

Results from the 1999-2000 survey, published in the Journal of the American Medical Association, show that almost two thirds of the population (64.5 per cent) is now officially rated overweight, with a body mass index (BMI) of 25 or more. That is equivalent to a weight of 11 stone (69kg) for a person 5ft 6in tall, or 12.4 stone (78kg) for a person 5ft 10in tall.

The proportion who are obese rose from 22.9 per cent to 30.5 per cent in the 1988-94 survey. "Obese" is defined as a BMI of 30 or over, equivalent to a weight of 13.2 stone (83kg) for a person 5ft 6in tall or 14.7 stone (91kg) for a person 5ft 10in tall.

Younger men and women, aged under 40, were the fastest to put on weight. The proportion of obese men under 40 has leapt in the past decade from one in seven to almost one in four. The increase in young people's weight is especially worrying because the risk of health problems is linked with the length of time a person is overweight. The earlier in life a person becomes obese the greater the risk of developing chronic conditions including diabetes, arthritis and heart disease.

The authors, based at the Centres for Disease Control in Hyattsville, Maryland, say that although the increases appear dramatic they are part of a long-term trend affecting all affluent and well-nourished societies. "It is likely to be difficult to reverse the increasing prevalence of overweight and obesity in the United States," they say.

In Britain, scientists warned last month that young people raised on fast food and leading sedentary lives could die before their parents. The combination of a superabundance of food and increasing idleness meant a pandemic of obesity was inevitable, a conference of the British Association for the Advancement of Science was told.

A spokesman for the International Obesity Taskforce, based in the UK, said rates of obesity were increasing even faster in Britain and could catch up with those in America. The proportion of the population who are obese has increased threefold to 21 per cent since 1980. The taskforce warned last month that obesity could overtake smoking as Britain's biggest preventable killer within 10 to 15 years.