Treating obesity-related disorders costs as much or more than illnesses caused by aging, smoking and problem drinking.

It accounts for 2 percent of the national health expenditure in France and Australia, more than 3 percent in Japan and Portugal and 4 percent in the Netherlands.

A review of research into the economic causes and consequences of obesity presented at the 14th European Congress on Obesity showed that in 2003 up to $96.7 billion was spent on obesity problems in the United States.

"An increase in the prevalence of obesity increases the healthcare costs," Anne Wolf of the University of Virginia School of Medicine said.

"As age increases so do healthcare costs for obesity."

Obesity, which is a risk factor for chronic diseases like diabetes, is calculated using the body mass index (BMI) -- dividing weight in kilograms by height in meters squared.

A BMI of more than 30 is considered obese, more than 40 is very severe.

The costs of dealing with the consequences of obesity rise along with the severity of the disorder. Being overweight or obese increases the odds of suffering from diabetes, cardiovascular disease and osteoarthritis which are the major reasons for obesity healthcare costs.

"Each unit increase in BMI is associated with a 2.3 percent cost increase," said Wolf.

Although most of the cost analysis for obesity has been done in the United States, where about 30 percent of adults are obese, Wolf said the figures would be comparable for other western countries with rising rates of obesity.

An estimated 10-20 percent of men and 10-25 percent of women in European countries are obese.

Along with hefty health costs, obesity is also associated with a greater loss of productivity and increased rates of disability.

Studies in the United States have shown that about 6 percent of people with a healthy weight are unable to work but the figure rises to 10 percent or more among the obese.

Much of the healthcare spending on obesity-related problems is due to prescription drug costs and more hospital stays.

Obese patients are more likely to require medication for diabetes, cardiovascular disease, pain relief, asthma and other illnesses than people with a normal weight, according to Wolf.

Despite the health and economic consequences of obesity, which affects more than 300 million people worldwide including a growing number of children and adolescents, health experts believe it is one of the most neglected public health issues.

"It is a very serious problem," said Wolf. "The excess costs of obesity are present in all ages."