Definition of Type 2 diabetes:

Type 2 diabetes is a chronic (lifelong) disease marked by high levels of sugar in the blood. It begins when the body does not respond correctly to insulin, a hormone released by the pancreas. Type 2 diabetes is the most common form of diabetes.

See also:

• Diabetes
• Gestational diabetes
• Type 1 diabetes

Causes, incidence, and risk factors:

Diabetes is caused by a problem in the way your body makes or uses insulin. Insulin is needed to move glucose (blood sugar) into cells, where it is used for energy.

If glucose does not get into the cells, the body cannot use it for energy. Too much glucose will stay in the blood, causing the symptoms of diabetes.

There are several types of diabetes. This article focuses on type 2, which usually occurs with obesity and insulin resistance.

Insulin resistance means that fat, liver and muscle cells do not respond normally to insulin. As a result they do not store sugar for energy. Since the tissues do not respond well to insulin, the pancreas produces more and more insulin.

Because sugar is not getting into the tissues, abnormally high levels of sugar build up in the blood. This is called hyperglycemia. Many people with insulin resistance have hyperglycemia and high blood insulin levels at the same time. People who are overweight have a higher risk of insulin resistance, because fat interferes with the body's ability to use insulin.

Type 2 diabetes usually occurs gradually. Most people with the disease are overweight at the time of diagnosis. However, type 2 diabetes can also develop in those who are thin, especially the elderly.

Family history and genetics play a large role in type 2 diabetes. Low activity level, poor diet, and excess body weight (especially around the waist) significantly increase your risk for type 2 diabetes.

Other risk factors include:

• Age greater than 45 years
• HDL cholesterol of less than 35 mg/dL or triglyceride level of greater than 250 mg/dL
• High blood pressure
• History of gestational diabetes
• Previously identified impaired glucose tolerance by your doctor
• Race/ethnicity (African Americans, Hispanic Americans, and Native Americans all have high rates of diabetes)