Insulin resistance refers to the inability of the body tissues to respond properly to insulin. Insulin lets sugar (glucose) enter body cells, where it is used for energy. Insulin also helps muscles, fat, and liver cells store sugar to be released when it is needed. If the body tissues do not respond properly to insulin, the blood sugar level rises.

Insulin resistance may cause the pancreas to release too much insulin (hyperinsulinemia). It may also cause the liver to release too much sugar into the blood.

Several factors may increase insulin resistance, including:

• Family history. Insulin resistance may run in families.
• Being overweight. The more a person weighs, the more insulin his or her pancreas makes and the less the person's body cells respond to insulin. People who are overweight mostly in the upper body have greater insulin resistance and have the greatest risk of developing type 2 diabetes.
• Lack of exercise. People who get little or no exercise often have much greater insulin resistance than people who exercise on a regular basis.
• Age. Teens and older adults usually have greater insulin resistance. Teens have greater insulin resistance because of growth hormones.
• Pregnancy. In the last 3 to 4 months of pregnancy (third trimester), insulin resistance is increased. A woman who did not have diabetes before pregnancy can develop a type called gestational diabetes.