AMERICAN waistlines are expanding relentlessly despite a glut of diet plans, health crazes and a boom in personal fitness trainers, according to the latest research. Health experts say obesity is the second biggest preventable killer in the US after smoking.
While a minority of US citizens spend every lunchtime pounding the pavement and every evening sipping health juices, many more are sedentary and fat, the National Centre for Disease Prevention said. Thirty five per cent of adults were defined as "dangerously overweight" in 1994 - up from 25 per cent in 1980, when the last comprehensive poll was conducted.
"The hard data shows us that people are eating more and doing less," said Ms Sylvia Ogden, coordinator of the nationwide survey of 40,000 people, "so they get fatter."
Changes in lifestyle which have reduced levels of activity - more car journeys, more office jobs - together with an apparently unstoppable rise in average calorie consumption have pushed more and more Americans into unhealthy territory, the centre said.
Black and Mexican American women are the worst affected, with more than one in two respondents overweight.
Ms Ogden said the findings were in stark contrast to the image of a Lycra clad energetic nation. "It is kind of strange," she said. One explanation is that ordinary mortals are intimidated by the regimes of the super fit. Oprah Winfrey is slim, but she runs five miles a day.
"It is a concern that people will be put off by this kind of thing," said Ms Ogden.
The number of children and adolescents who are overweight has doubled as computer games and TV take over from street soccer and as wary parents ban outdoor play.
According to the National Tasks Force on the Prevention of Obesity, the condition is claiming 300,000 lives a year and costing the economy (£43.8 billion) in lost working days and lower productivity. Heart disease, diabetes and high blood pressure are all exacerbated by being overweight.
Americans spend $30 billion a year on diet books and kits in an effort to shed fat, but experts warned of the dangers of a diet a binge cycle, pointing out that most weight reduction plans were ultimately unsuccessful. "Prevention is better than cure," said Ms Ogden.
Men now consume an average of 2,684 calories a day, up from 2,457 in 1980. The average woman's daily calorie intake has jumped from 1,531 to 1,805. Meanwhile, the numbers engaging in any form of physical activity is low: 59 per cent of women and 49 per cent of men report no exercise at all in their weekly routine.