Causes of Type 2 Diabetes

Diabetes is a number of diseases that involve problems with the hormone insulin. While not everyone with type 2 diabetes is overweight, obesity and lack of physical activity are two of the most common causes of this form of diabetes. It is also responsible for nearly 95% of diabetes cases in the United States, according to the CDC.

This article will give you a better understanding of the causes of type 2 diabetes, what happens in the body when type 2 diabetes occurs, and specific health problems that increase the risk of type 2 diabetes. Each section links to more in-depth information on that topic.

In a healthy person, the pancreas (an organ behind the stomach) releases insulin to help the body store and use the sugar from the food you eat. Diabetes happens when one of the following occurs:

  • When the pancreas does not produce any insulin.
  • When the pancreas produces very little insulin.
  • When the body does not respond appropriately to insulin, a condition called "insulin resistance."

Unlike people with type 1 diabetes, people with type 2 diabetes produce insulin; however, the insulin their pancreas secretes is either not enough or the body is unable to recognize the insulin and use it properly (insulin resistance). When there isn't enough insulin or the insulin is not used as it should be, glucose (sugar) can't get into the body's cells and builds up in the bloodstream instead. When glucose builds up in the blood instead of going into cells, it causes damage in multiple areas of the body. Also, since cells aren't getting the glucose they need, they can't function properly.

The Role of Insulin in the Cause of Type 2 Diabetes

To understand why insulin is important, it helps to know more about how the body uses food for energy. Your body is made up of millions of cells. To make energy, these cells need food in a very simple form. When you eat or drink, much of the food is broken down into a simple sugar called "glucose." Then, glucose is transported through the bloodstream to these cells where it can be used to provide the energy the body needs for daily activities.

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The amount of glucose in the bloodstream is tightly regulated by insulin and other hormones. Insulin is always being released in small amounts by the pancreas. When the amount of glucose in the blood rises to a certain level, the pancreas will release more insulin to push more glucose into the cells. This causes the glucose levels in the blood (blood glucose levels) to drop.

To keep blood glucose levels from getting too low (hypoglycemia or low blood sugar), the body signals you to eat and releases some glucose from the stores kept in the liver; it also signals the body to lower the amount of insulin being released.

People with diabetes either don't make insulin or their body's cells no longer are able to recognize insulin, leading to high blood sugars. By definition, diabetes is having a blood glucose level of greater than or equal to126 milligrams per deciliter (mg/dL) after an overnight fast (not eating anything), or by having a non-fasting glucose level greater than or equal to 200 mg/dL along with symptoms of diabetes, or a glucose level of greater than or equal to 200 mg/dL on a 2-hour glucose tolerance test, or an A1C greater than or equal to 6.5%. Diabetes must be confirmed by meeting at least two of these test criteria, or by repeating one of these tests on a different day.

Health Risk Factors for Type 2 Diabetes

Type 2 diabetes is believed to have a strong genetic link, meaning that it tends to run in families. Several genes are being studied that may be related to the cause of type 2 diabetes. If you have any of the following type 2 diabetes risk factors, it’s important to ask your doctor about a diabetes test. With a proper diabetes diet and healthy lifestyle habits, along with diabetes medication, if necessary, can manage type 2 diabetes just like you manage other areas of your life. Be sure to continue seeking the latest information on type 2 diabetes as you become your own health advocate.

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Other type 2 diabetes risk factors include the following:

  • High blood pressure
  • High blood triglyceride (fat) levels
  • Gestational diabetes or giving birth to a baby weighing more than 9 pounds
  • High-fat and carbohydrate diet
  • High alcohol intake
  • Sedentary lifestyle
  • Obesity or being overweight
  • Ethnicity: Certain groups, such as African Americans, Native Americans, Hispanic Americans, and Asian Americans, have a greater risk of developing type 2 diabetes than non-Hispanic whites.
  • Aging: Increasing age is a significant risk factor for type 2 diabetes. The risk of developing type 2 diabetes begins to rise significantly at about age 45, and rises considerably after age 65.

WebMD Medical Reference Reviewed by Michael Dansinger, MD on May 14, 2015

Sources

SOURCES: 

American Diabetes Association: "Insulin and Low Blood Glucose." 

American Diabetes Association: "Stomach Fat and Insulin Resistance." 

National Diabetes Information Clearinghouse: "Your Guide to Diabetes:  Type 1 and Type 2." 

Forouhi, N. Diabetologia, 2006; 49:822. Kim, SH. Journal of the American College of Cardiology, 2006; 48:293. 

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