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 then remain in the blood, causing the symptoms of diabetes.
There are several types of diabetes. This article focuses on type 2, which is usually accompanied by obesity and insulin resistance.
Insulin resistance means that insulin produced by your pancreas cannot get inside fat and muscle cells to produce energy. Since the cells are not getting the insulin they need, the pancreas produces more and more. Over time, 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:
Race/ethnicity (African-Americans, Hispanic-Americans, and Native Americans all have high rates of diabetes)
Age greater than 45 years
Previously identified impaired glucose tolerance by your doctor
High blood pressure
HDL cholesterol of less than 35 mg/dL or triglyceride level of greater than 250 mg/dL
History of gestational diabetes.