The odds are worse for black and Hispanic children: nearly half of them are likely to develop the disease, said Dr. K.M. Venkat Narayan, a diabetes epidemiologist at the CDC.
"I think the fact that the diabetes epidemic has been raging has been well known to us for several years. But looking at the risk in these terms was very shocking to us," Narayan said.
The 33 percent lifetime risk is about triple the American Diabetes Association's current estimate.
The implications are frightening. Diabetes leads to a host of problems, including blindness, kidney failure, amputation and heart disease, and diabetics are getting younger and younger.
Including undiagnosed cases, authorities believe about 17 million Americans, nearly 6 percent of the U.S. population, have diabetes today.
If the CDC predictions are accurate, some 45 million to 50 million U.S. residents could have diabetes by 2050, said Dr. Kevin McKinney, director of the adult clinical endocrinological unit at the University of Texas Medical Center in Galveston.
"There is no way that the medical community could keep up with that," he said.
McKinney, who was not part of the study, said Narayan's procedures are valid and the estimates, being presented Saturday to the American Diabetes Association, are probably all too likely.
Diabetes, a disease caused largely by obesity and lack of exercise, has been an increasing worry for decades. From the mid-1960s to the mid-'90s, the number of cases tripled.
Dr. Bill Releford of the Diabetes Amputation Prevention Foundation told CBS News, "I think the 39-cent hamburger is the real weapon of mass destruction."
The number of diagnosed cases of diabetes rose by nearly half in just the past 10 years, hitting 11 million in 2000, and is expected to rise an additional 165 percent by 2050, to 29 million, an earlier CDC study by Narayan and others found.
"These estimates I am giving you now are probably quite conservative," Narayan said in an interview before the diabetes association's annual scientific meeting here.
Narayan said it would be difficult to say whether undiagnosed cases would rise at the same rate. If they did, that could push the 2050 figure to 40 million or more.
Doctors had known for some time that Type 2 diabetes - what used to be called adult-onset diabetes because it typically showed up in middle-aged people - is on the rise, and that patients are getting younger.
"Type 2 diabetes was something people got when they were 40, because they were overweight. Now 10, 11, 12-year-olds... these kids that are overweight are at very high risk for diabetes," said research dietician Mary Savoye in an interview with CBS News.
Nobody had crunched the numbers before to look at current odds of getting the disease, Narayan said.
Overall, he said, 39 percent of the girls who now are healthy 2½-to 3-year-olds and 33 percent of the boys are likely to develop diabetes, he said.
For Hispanic children, the odds are closer to one in two: 53 percent of the girls and 45 percent of the boys. The numbers are about 49 percent and 40 percent for black girls and boys, and 31 percent and 27 percent for white girls and boys.
To reach his estimates, Narayan used data from the annual National Health Interview Survey of about 360,000 people from 1984-2000, from the U.S. Census Bureau and from a previous study of diabetes as a cause of death.
Globally, the World Health Organization has estimated that by 2025, the number of people with diabetes worldwide will more than double, from 140 million to 300 million.
"They estimated that by 2025, there would be close to 60 million people with diabetes in India alone. That's about the size of Great Britain or France," Narayan said.
It doesn't have to happen.
Type 2 diabetes can be prevented or delayed by losing weight, exercising and following a sensible diet.
A study two years ago found that walking 30 minutes a day most days of the week and losing a little weight helped the people most likely to get it cut their risk 58 percent.
The U.S. Department of Health and Human Services used that information last fall in its "Small Steps, Big Rewards" campaign against diabetes.