Almost 24 million Americans have diabetes according to the Center for Disease Control (CDC). Millions of more Americans have a condition that puts them at high risk for developing diabetes. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) estimates that almost 57 million American adults have pre-diabetes. Pre-diabetes, also known as impaired glucose tolerance, means having a blood sugar level that is higher than normal, but not yet persistently high enough to be considered type 2 diabetes.

There's good news, though. If you have pre-diabetes, you can delay or prevent type 2 diabetes by losing weight and getting regular exercise.

Risks of pre-diabetes

If you have pre-diabetes, you are at 50 percent higher risk for developing heart disease and stroke, according to the American Diabetes Association (ADA). These are risk factors for pre-diabetes:

• Overweight or obesity; a body mass index (BMI) of 25 to 29.9 is considered overweight, and a BMI of 30 or higher is obese

• A family history of type 2 diabetes

• Being an African American, American Indian, Hispanic American or Asian American

• Low HDL cholesterol and high triglycerides (abnormal lipid profile)

• High blood pressure

• A history of gestational diabetes

What to do

If you have pre-diabetes, work with your health care provider on lifestyle changes you can make. If you're overweight, losing weight can reduce your risk for type 2 diabetes. Losing even eight to 10 pounds can make a difference, the NIDDK says.

Ultimately, you should aim for a BMI of 27; ideally, less than 25.

To lose weight, maintain the loss and live a healthier life, get regular moderate-intensity exercise. The U.S. Department of Agriculture's 2005 guidelines on nutrition and exercise recommend 30 to 60 minutes of moderate to vigorous exercise daily. This amount can be broken up into several 20-minute sessions each day. Be sure to check with your health care provider before beginning an exercise program.

By the numbers

Two types of tests can determine whether you have pre-diabetes: fasting plasma glucose test (FPG) or the oral glucose tolerance test (OGTT). If your blood sugar level is abnormally high with the FPG, you have impaired fasting glucose, according to the ADA. If your blood sugar levels are abnormally high with the OGTT, you have impaired glucose tolerance.

Here's what overnight (or eight hours or more) fasting blood sugar numbers mean, according to guidelines by the CDC. Doctors measure blood sugar in milligrams per deciliter (mg/dL):

• Normal: Below 100 mg/dL

• Pre-diabetes: 100 to 125 mg/dL

• Diabetes: 126 mg/dL and above

Here is what oral glucose tolerance blood sugar numbers mean, according to the ADA:

• Normal: Below 139 mg/dL

• Pre-diabetes: 140 to 199 mg/dL

• Diabetes: 200 mg/dL and above