WASHINGTON - The number of Americans with diabetes will nearly double over the next 25 years, rising from 23.7 million in 2009 to 44.1 million in 2034, according to a study by the University of Chicago.

In the same period, medical costs associated with treating the disease will triple from US$113 billion to US$336 billion dollars, even without a rise in the incidence of obesity, according to the study published in the December issue of Diabetes Care.

"If we don't change our diet and exercise habits or find new, more effective and less expensive ways to prevent and treat diabetes, we will find ourselves in a lot of trouble as a population," said lead author Elbert Huang.

The study said its projections, despite being significantly higher than other recent estimates, may be too conservative because they assume the rate of diabetes and obesity, a risk factor for the disease, will remain stable.

In 1991, scientists projected that the number of Americans with diabetes would reach 11.6 million people in 2030, but some 20 years before that date the figure is already double that.

The study's authors acknowledge that obesity rates have risen steadily in past years, but predict that they will level out over the next decade and then decline slightly from the current 30 percent level to around 27 percent in 2033.

The US health program Medicare, which provides health care for older Americans, spends some US$45 billion a year on diabetes treatment for 8.2 million people.

By 2034, the number of people with diabetes covered by the program is expected to rise to 14.6 million, according to the study, with associated costs rising to US$171 billion a year.