Los Angeles, March 5 (Xinhua) The American Diabetes Association (ADA) has warned that the diabetes threat is greater than feared.

The number of new cases of type 2 diabetes among middle aged Americans has doubled over the past three decades, fuelled largely by increasing rates of obesity, the ADA said.

An estimated two-thirds of adult Americans are now overweight or obese.

The world can now expect many more people to succumb to this chronic disease than originally anticipated, said the organisation in a new study.

According to the latest World Health Organization (WHO) estimates, the number of people worldwide with diabetes climbed from 30 million in 1985 to 171 million in 2000.

Some 4-6 percent of adults aged 20 and over are now affected. Developed nations tend to have a higher prevalence but developing nations are fast catching up.

There was a 69 percent increase from 5.2 percent to 8.8 percent in diabetes prevalence from 1995 to 2005, exceeding the WHO's estimate of a 60 percent global rise between 1995 and 2030 and 39 percent between 2000 and 2030.

In Canada, for example, diabetes prevalence was supposed to grow 65 percent between 1995 and 2030.

'I regrettably have to confess that this did not surprise me,' said Larry Deeb, president of medicine and science at ADA.

'Every estimate I have ever seen for prevalence has been surpassed the next time you get a chance to look. It's quite frightening,' he said.

According to statistics provided by the ADA, by last year, the number of people with diabetes in Ontario, Canada, had already surpassed the rate predicted for 2030 by the World Health Organization.

'Our paper indicates that the magnitude of the problem is such that our health-care systems across the world are going to have an increasingly difficult time managing the ongoing increase in diabetes,' said Lorraine Lipscombe, lead author of the study, and a research fellow at the Institute for Clinical Evaluative Sciences in Toronto.

'We really have to start adopting more aggressive prevention approaches, otherwise, we will see rates continue to increase. And it will be unmanageable.'

Type 2 diabetes, a condition in which the body either doesn't produce enough insulin or the cells ignore the insulin, is one of the most costly and burdensome diseases. Left untreated, it can result in heart disease, blindness, amputations as well as nerve and kidney damage.