VIENNA Airline pilots, truck drivers and rail workers are more likely to suffer from diabetes and heart disease because of the stress, tension and shift work their jobs involve, Reuters reported on Friday.

Long hours of immobility piloting a plane or driving a bus or train, coupled with odd eating patterns and working around the clock, contribute to an unhealthy lifestyle, excess weight and a greater chance of developing obesity-related diseases.

Dr. Svetoslav Handijev of the Department of Nutrition at the Transport Medical Institute in Bulgaria told scientists at an obesity conference that many transport workers were overweight and obese.

"A transport worker's job -- high tension, low physical activity, unbalanced nutrition, relative immobility, high speed travel, shift work and environmental factors -- can contribute to the development of metabolic and cardiovascular diseases," Handijev said.

He and his colleagues compared the body mass index (BMI) -- a standard method of measuring obesity -- cholesterol and blood sugar levels and blood pressure of 5,659 Bulgarian transport employees with those of the general population.

More than 65 percent of transport workers were found to be either overweight or obese. They also had higher levels of type 2, or adult onset diabetes, and heart disease than people in other occupations.

"The diseases are found significantly more often in transport workers with overweight and obesity than those with normal BMI," Handijev said.

BMI is measured by dividing weight in kilograms by height in meters squared. A BMI of more than 30 is considered obese. More than 35 is severely obese and more than 40 is very severe.

More than 57 percent of diabetes cases and 17 percent of coronary heart disease are attributable to obesity, which is also a risk factor for high blood pressure, stroke, joint problems and colon, breast and uterine cancers.

According to the World Health Organization (WHO) more than 300 million people around the world are obese. It sees changes in diet, life style and work as the main causes of the problem.

Professor Jaap Seidell, a Dutch epidemiologist who has worked with the WHO on obesity, said it was set to be the biggest single disease of the century.

"It may be doubling over the next 20 years," he warned the 11th European Congress on Obesity, adding that preventive measures were needed to curb the problem.

Obesity is a chronic disease. Experts attending the four-day meeting said a combination of better diets with less fat and more fruit and vegetables, more exercise, behavior modification, drug therapy and in very severe cases surgery were used to help the obese lose weight.