America gets fatter

Americans spend too much time at their computers

More than a half of all adult Americans are overweight, according to a new assessment of obesity in the United States.

The National Heart, Lung and Blood Institute (NHLBI) has classified 55% of adult Americans, or 97 million adults, as overweight or obese. This compares to 43% in 1960.

Karen Donato, who helps co-ordinate obesity education at the NHLBI, said people were eating more, exercising less, and being fooled by "low fat" foods.

"When people read labels, they're more likely to notice what's low fat and 'healthy' but may not be looking at calories," she said.

In addition to the extra calories being taken in, Ms. Donato said, culprits in the national weight gain include "too much time sitting at our computers, driving the car, watching television and taking the elevator instead of the stairs."

Diagnosis and treatment

In the population as a whole, 22.5% of Americans are now classified as clinically obese. This figure stood at 13% in 1960. Most of the increase has taken place in the last ten years according to the survey data.

The NHLIB has established the first-ever federal government guidelines on diagnosing and treating overweight and obese people. They bring US standards into line with the rest of the world by reclassifying the definition of obesity on the body mass index (BMI) - a calculation used to determine who weighs too much.

It is worked out by dividing a person's weight in kilograms by their height in metres squared.

Most health experts around the world, and many in the United States, had long agreed that a person with a BMI of 25 was overweight and someone with a BMI of 30 or more was obese.

But the NHLBI had, in the past, let a person get up to a BMI of 27 before he or she was considered overweight.

Waisteline indicator

The guidelines also use waist circumference. Any man with a waist more than 40 inches around and any women with a waist of 35 inches or bigger are at risk if they are also overweight. This is because fat deposited in the abdomen is more indicative of health problems than fat elsewhere in the body.

"The guidelines tell the truth about the risks associated with unhealthy weight," Dr. Xavier Pi-Sunyer, who headed the panel that wrote the guidelines, said.

People who are overweight risk higher blood pressure, high blood cholesterol, diabetes and, possibly, some cancers.

The guidelines advise doctors to measure cholesterol, blood sugar and take into account a family history of obesity-related disease when seeing overweight patients to assess their real risk of illness.