ATLANTA, Jan. 26 (UPI) -- Nearly 26 million Americans have diabetes, but an estimated 79 million adults have prediabetes, U.S. health officials say.

The estimates by the Centers for Disease Control and Prevention in Atlanta say prediabetes is a condition in which blood sugar levels are higher than normal, but not high enough to be diagnosed as diabetes. However, prediabetes raises a person's risk of type 2 diabetes, heart disease and stroke. Prediabetes affects 35 percent of adults age 20 and older.

"These distressing numbers show how important it is to prevent type 2 diabetes and to help those who have diabetes manage the disease to prevent serious complications such as kidney failure and blindness," Ann Albright, director of CDC's division of diabetes translation, says in a statement.

"We know that a structured lifestyle program that includes losing weight and increasing physical activity can prevent or delay type 2 diabetes."

In 2008 the CDC estimated 23.6 million Americans, or 7.8 percent of the population, had diabetes and another 57 million adults had prediabetes.

The 2011 estimates have increased partly because Hemoglobin A1c is now used as a diagnostic test and was used for the calculations for the first time. The test measures levels of blood glucose over a period of two to three months and because of this change, estimates of populations with diabetes and prediabetes in the 2011 fact sheet are not directly comparable with previous estimates, Albright says.