Greatly increasing a prediction made just three years ago, the CDC now predicts 48.3 million Americans will have diabetes by 2050.

That's triple the number of people living with diabetes today -- and 9.3 million more than the CDC forecast in 2003.

The new figures come from K.M. Venkat Narayan, MD, and his CDC colleagues. Narayan, formerly chief of the CDC's diabetes epidemiology and statistics branch, is now at Emory University's Rollins School of Public Health.

"The numbers are very worrying," Narayan tells WebMD. "There is an epidemic going on that -- if left unchecked -- will have a huge effect on the U.S. population and on health care costs."

The new numbers sound an alarm, says Ronald B. Goldberg, MD, chief of the Diabetes Research Institute at the University of Miami Leonard M. Miller School of Medicine.

"This worsens the predictions that all of us have been making about the future problem that diabetes is going to represent, not only in the U.S. but around the world," Goldberg tells WebMD. "The consequences are more and more suffering -- eye complications, amputations, and markedly more heart disease … And just from an economic point of view, it will cripple our health care budgets."

The new calculations appear in the September issue of Diabetes Care.

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By the middle of the century, Narayan's team predicts, diabetes will increase by 481 percent among Hispanics, 208 percent among blacks, and 113 percent among whites.

One reason for the increase is that, with better care, people with diabetes are living longer. But that accounts only for about a tenth of the growth; the ongoing rise in new diabetes cases accounts for almost 90 percent of the spiral upwards.

As scary as these numbers are, they assume the rate of new cases will level off at 2004 levels. If this doesn't happen, we can expect to see yet another leap in diabetes predictions.

Will this happen? Diabetes is being driven by the obesity epidemic. So far, the needle on the scale has been going up, not down.

And Goldberg points to a scary trend: Once people have diabetes, they have it for life -- and there's been an increase in young people getting the disease.

"We are going to see a greater prevalence of young adults getting this disease, which means this explosion of diabetes is going to have an even larger impact on lifespan and national productivity," Goldberg says.

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The Good News

Narayan, an optimist, sees a silver lining in the gathering clouds. The huge increase in future diabetes cases results from a relatively small uptick in the rate at which new cases are being diagnosed.

This means a small decrease in the rate would have a correspondingly huge effect in lowering future diabetes cases.

Narayan points to studies showing that, with help and encouragement, people with prediabetes can regain healthy blood sugar levels.

"There are effective interventions available," he says. "If we could apply those interventions across the country, we could slow down the diabetes rate. That is the message here for me."

The interventions Narayan has in mind are designed to get people to stop gaining weight and to become more active. People can do this -- but advice isn't enough. It takes an intensive effort to teach people the skills they need and to stay in touch to keep them motivated.

That kind of program costs money -- but much less than a diabetes epidemic spiraling out of control.

"These programs would have a major impact," Goldberg says. "We have to find better methods of funding them at the federal, state, and local level. And then, once a person has diabetes, there has to be more focus on how to prevent complications. We have made some progress, but unfortunately not enough."

"If delivered early in life, the benefits of these interventions -- improving health, reducing diabetes -- are worth investing in," Narayan says. "And the individual benefits, too. By preventing or postponing diabetes, you prevent a considerable amount of disability later in life."

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By Daniel J. DeNoon, reviewed by Louise Chang, MD

SOURCES: Narayan, K. Diabetes Care, September 2006; vol 29: pp 2114-2116. K.M. Venkat Narayan, MD, professor of global health and epidemiology, Rollins School of Public Health, Emory University, Atlanta. Ronald B. Goldberg, MD, professor of medicine and chief of the Diabetes Research Institute, University of Miami Leonard M. Miller School of Medicine.