Ask The Expert
Diagnosis & Symptoms

Insulin resistance is one of the most significant defects in type 2 diabetes, and yet many people do not really know what it is. The simple definition would be:

• A condition in which insulin isn’t working effectively, or
• An underlying cause of type 2 diabetes, when your body has difficulty using the insulin it makes or the insulin you inject.
• There is also a more rare condition in some people with type 1 diabetes, when their body produces antibodies against the injected insulin, so they must inject abnormally large amounts of insulin to control their blood sugars. Most people with type 1 diabetes require much less than 100 units of insulin per day but, with this condition, they may require 200 or more units per day. As this is a rare situation, it will not be discussed further in this answer.

How the body uses glucose:

• The cells in your body need glucose to function. Every time you eat, the level of glucose in your blood rises. Four to five hours after a meal, your blood glucose level returns to baseline. When you haven’t eaten for a while and during the night when you are sleeping, your liver releases stored glucose to supply you with energy.
• Insulin is released in response to glucose in the blood.

Insulin has 3 main roles:

1. Regulates the liver from releasing too much glucose (I like to say that insulin leans up against the door of the liver and only lets a little glucose out at a time). When there is enough glucose in the blood, insulin tells the liver to shut down its production of glucose.
2. Acts as a “doorman, or key” to open the doors of the cells (called receptors) and to allow glucose to enter the cells so the glucose can then be turned into energy.
3. Acts as a “traffic cop,” directing some of the glucose to be stored back into the liver and the muscles, and if you eat more than you need, the excess energy is stored as fat.

What happens with insulin resistance?

• The liver continues to release glucose, even when insulin is telling it to “close the door.”
• There are various defects at the receptor level: there are not enough receptors; or more commonly, there is a defect in how insulin binds to the receptor; also there is a defect in how the glucose is transported into the cell, and utilized once it gets inside the cell. I explain this by saying, “either there aren’t enough doors on the cell, or the doors are locked and the key doesn’t fit, plus once the glucose gets through the door, it doesn’t know what to do.”

What causes, or is associated with, insulin resistance?

• Genetics
• Obesity (although some normal weight individuals also have insulin resistance).
• Abnormalities in glucose transporters, which are supposed to move glucose into the cells. Studies show that some people are deficient in a glucose transporter called GLUT4 and, interestingly, exercise increases GLUT4.
• Researchers can’t agree on whether the underlying cause of type 2 diabetes is insulin resistance or a defect in insulin secretion, but either condition can lead to the other (i.e. which came first, the chicken or the egg?). For example, if you have insulin resistance, blood glucose rises, since it can’t adequately get into the cells; this causes the pancreas to release more insulin; often, in early stages of type 2 diabetes, there are abnormally large amounts of insulin circulating in the blood; but over time, the pancreas is unable to produce enough insulin.
• Stress, infection, severe illness, or steroid use can temporarily increase blood glucose and contribute to insulin resistance.
• Smoking
• Cardiometabolic risk: This is a term describing factors such as being overweight, having type 2 diabetes, high cholesterol, high blood pressure, and insulin resistance: any of these factors can increase your risk of heart disease.

What can you do to treat insulin resistance?

• Exercise: physical activity increases the body’s sensitivity to insulin, up to one day after the activity. Also, resistance training, i.e. weight lifting (which increases muscle mass) helps the body use glucose more effectively.
• Lose Weight: even a small amount of weight loss has been shown to decrease insulin resistance.
• Stop smoking: In addition to increasing your risk of cancer and cardiovascular disease, smoking contributes to insulin resistance. Quitting smoking is not easy, but it is a very important thing to do to improve your health.
• Drug therapy: The category of drugs called Biguanides targets insulin resistance in the liver, decreasing the liver’s production of glucose. The category of drugs called Thiazolidinediones reduces insulin resistance by making muscle and fat cells more sensitive to insulin.

As you can see, researchers are constantly learning more about the causes and treatments for diabetes, and there are many tools available to help you manage your diabetes, using physical activity, nutrition, and medication.