Insulin Resistance

Insulin resistance is a condition associated with type 2 diabetes in which the body is unable to use the insulin it makes in the pancreas effectively. It is common in type 2 diabetes that insulin production by the pancreas is also decreased. This decreased insulin production combined with insulin resistance results in elevations in blood glucose. Being overweight starts the process of events inside the body that leads to the development of insulin resistance.1,2

The process that leads to the development of type 2 diabetes, involving insulin resistance and loss of the ability to produce insulin, can begin well before a person is diagnosed with type 2 diabetes. In many people, insulin resistance and decreased insulin production develops over a period of 5 to 10 years before high blood sugar is detected.3

Learn more about the role of insulin in the body.

In a person with insulin resistance, cells cannot absorb glucose from blood. This sends the message to the beta cells to create and pump out increased amounts of insulin. Blood glucose levels may remain within the normal ranges as long as beta cells in the pancreas can meet the increased demand for insulin. However, over time as beta cells fail to keep up with demand, excess blood glucose can lead to prediabetes and type 2 diabetes.

What causes insulin resistance?

Two major factors are known to contribute to the development of insulin resistance and type 2 diabetes. These include being overweight or obese and lack of physical activity. Other important factors that play a role include ethnicity, old age, problems affecting sleep, smoking, and use of certain medications.4

Being overweight or obese. Being overweight having a body mass index [BMI] between 25 and 29.9) or obese (having a BMI of 30 or higher) is recognized as a key cause of insulin resistance. This is especially true in individuals where excess weight is concentrated in the area of the waist/abdomen/central weight. Fat tissue has been found to produce hormones and other chemicals that contribute to insulin resistance, as well as causing other health problems including cardiovascular disease, high blood pressure, and abnormal blood lipids.4

Location of excess fat on the body is important when it comes to risk for insulin resistance. Even if your BMI is in the normal range, if you are a man and have a waist measurement of 40 inches or greater or a women and have a waist measurement of 35 inches or greater, you may be at increased risk for insulin resistance.4

Lack of physical activity. Results from numerous studies have shown that lack of physical activity can be a factor in the development of insulin resistance and, over time, the development of type 2 diabetes. The muscles of the body use more glucose than any other type of tissue. In fact, after regular physical activity (when muscle cells have depleted their store of glucose), muscles have increased sensitivity to insulin and can even absorb glucose without the aid of insulin. The more muscle mass the body has, the greater its ability to use glucose and keep blood glucose levels in the normal range.4

Fatty tissue, particularly in the area of the belly, has been shown to promote chronic inflammation in the body. Studies have found that fat tissue attracts immune cells and can trigger an immune response and chronic inflammation. This inflammation contributes to insulin resistance and can cause serious damage throughout the body over time, often without any symptoms.4

Sleep problems and insulin resistance

Apart from lack of physical activity and obesity, sleep problems have been shown to play an important role in increasing risk for insulin resistance. Sleep apnea, a sleep disorder in which a person experiences pauses in breathing or shallow or infrequent breathing during sleep resulting in poor quality of sleep, has been linked closely to the development of insulin resistance and development of type 2 diabetes. Sleep problems such as sleep apnea, which can lead to excessive daytime drowsiness and fatigue, also increase the risk of obesity and type 2 diabetes.4 The Look AHEAD Study, a 4-year randomized, controlled trial conducted in 4,503 adults with type 2 diabetes who had a body mass index (BMI) of 25 or higher, found that obstructive sleep apnea affected 86% of a subgroup of participants at baseline.5

Insulin resistance and metabolic syndrome

Insulin resistance is closely related to metabolic syndrome (also called insulin resistance syndrome). Metabolic syndrome includes a list of body traits and health conditions, common in people who are overweight or obese, which can lead to the development of type 2 diabetes. To have metabolic syndrome, you must satisfy any 3 of the following criteria1:

  • Large waist size. A waist measurement of 35 inches or more for women and 40 inches or more for men.
  • Abnormally low levels of HDL cholesterol. Low levels of high-density lipoprotein (HDL) cholesterol, known as the “good” cholesterol, below 50 mg/dL for women and 40 mg/dL for men, or receiving medication for low HDL cholesterol.
  • Elevated triglycerides. Levels of triglycerides in blood of 150 mg/dL or greater or receiving medication for elevated triglycerides.
  • High blood pressure. Blood pressure of 130/85 mmHg or greater or receiving treatment for high blood pressure.
  • Elevated blood glucose. A fasting blood glucose measurement of 100 mg/dL or greater or receiving medication for elevated blood glucose.

Given the key role that being overweight or obese plays in increasing risk for type 2 diabetes, it is no wonder that other criteria for metabolic syndrome overlap to a large extent with some of the key risk factors for development of type 2 diabetes, including sedentary lifestyle (being physically inactive) and fat distribution in the waist-to-hip area.

Written by: Jonathan Simmons | Last reviewed: May 2014.
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