A Primer on Insulin Resistance

Health Writer
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Recent concerns about Americans' consumption of refined carbohydrates and added sugars have put the spotlight on how poor diet and obesity raise the risk of prediabetes and Type 2 diabetes. We know that obesity contributes to insulin resistance, but what exactly constitutes insulin resistance and how do you know if you are at risk? If you have a family history of diabetes, struggle with excess weight, or consume the typical western diet filled with processed and refined foods that are high in sugar, then it is crucial for you to learn about insulin resistance.

Understanding insulin

Insulin is a hormone that is produced by your pancreas. The pancreas contains little clusters of cells called islets and beta cells in the islets produce the insulin. Your digestive tract breaks down carbohydrates (fruits, vegetables and grains) into glucose which then enters your bloodstream. Insulin helps your body’s muscle, fat and liver cells access the sugar which provides energy to the cells. Insulin also helps your liver and muscle tissue to store excess glucose. Insulin can also signal the liver to produce less glucose. Sounds like some simple interactions, so what can go wrong?

For reasons that are still unclear, your body may start using insulin ineffectively. That means that all the glucose transported in your blood may no longer enter the cells in an efficient manner. Your pancreas can start to work overtime, with the beta cells putting out higher levels of insulin because it senses that the body’s cells are resisting the insulin and not unlocking to utilize the available glucose.  Initially the extra insulin may help, but ultimately the pancreas becomes over-worked and over time may start to put out less and less insulin (beta cells become exhausted), especially as the insulin resistance persists. That translates into persistently high levels of blood sugar (hyperglycemia) which means you are entering a prediabetes phase and ultimately, diabetes, if there is no effective intervention.

What makes the cells resistant to the insulin or “insulin resistant?”

The mechanism is not fully understood but scientists have identified excess weight and physical inactivity as major drivers of the process. Obesity, especially central belly fat, is believed to contribute to insulin resistance because the fat seems to cause inflammation that disrupts insulin’s effectiveness.  Belly fat may also produce hormones and other substances that seem to instigate health issues like insulin resistance, high blood pressure, cholesterol imbalances and cardiovascular disease (CVD). In the early stages of insulin resistance and prediabetes, and sometimes even in the presence of Type 2 diabetes, weight loss can usually reverse the condition.

In the case of physical inactivity, the mechanism behind insulin resistance seems to be the inactive muscle cells being less primed to access and burn available glucose (if you’re not moving you’re using far less energy). If you’re not exercising you also tend to have fewer muscle cells. If you do start to exercise, the muscles become more sensitive to insulin and glucose uptake and utilization of available sugar is improved. If you train with weights, you will also build more muscle mass, meaning you will have more need for the glucose, and glucose uptake will be improved.

Other contributors to insulin resistance include: smoking, sleep apnea, sleep problems in general (linked with weight gain), steroid use, certain medications, and certain ethnicities (Latino, African Americans, Native Americans and Asian Americans) have higher rates of insulin resistance.  In some cases an autoimmune process can contribute to insulin resistance.

Understanding how insulin resistance translates into prediabetes or diabetes

When insulin resistance occurs your blood sugar levels will remain persistently high. This sets the stage for prediabetes and ultimately Type 2 diabetes, by placing never-ending pressure on your insulin-producing beta islet cells. They will keep trying to put out more and more insulin in order to overcome the insulin resistance, but ultimately the beta cells will fatigue and fail. The loss of the beta cell function usually leads to full blown Type 2 diabetes. Unless treated, the constantly high blood sugar levels damage nerve cells and blood vessels, resulting in complications that include heart disease, stroke, blindness, kidney failure, and lower-limb amputations due to compromised circulation.  Once the beta cells die, they are gone for good.

Research suggests that most people with prediabetes will develop Type 2 diabetes within ten years, unless they change their lifestyle.

Defining prediabetes and diabetes

Blood tests to diagnose prediabetes and diabetes include a fasting blood sugar level (FBS), a one, two or three hour glucose tolerance test (GTT), and an A1C test, which is your average blood sugar level over the past two or three months.

  • An A1C between 5.7 and 6.4 percent is considered an indicator of prediabetes.
  • An A1C over 6.4 percent is considered a strong indicator of a diagnosis of diabetes.

A1C tests need additional confirmation with preferably an FBS and GTT study, preferably a two hour GTT.  This is often used to confirm gestational diabetes as well.

  • An FBS between 100 to 125 mg/dL is considered prediabetes.
  • An FBS over 126 mg/dL is considered to indicate diabetes.
  • A two hour GTT between 140 – 199 mg/dL is considered prediabetes.
  • A two hour GTT at or over 200 mg/dL is considered to indicate diabetes.

Sometimes your doctor will repeat one or more of these tests just to make sure that the diagnosis is clear cut.  If only one test is found to be abnormal, your doctor may decide to repeat the tests in a few months, monitoring you for any frank symptoms in the interim.

The good news

Just losing 5-7 percent of your body weight can reverse insulin resistance and usually prediabetes.  Making changes in your diet and beginning an exercise program is what most people need to reverse insulin resistance and intercept inevitable diabetes. Specifically:

  • A balanced, calorie-reduced diet rich in lean and plant-based proteins, healthy oils, whole grains, non-starchy vegetables, some fruits, and select dairy products can help with weight loss.  The DASH Diet is one approach that can help to modify insulin resistance.  Your doctor may refer you to a nutritionist or dietician to learn more about carbohydrate “counting” and other dietary approaches.
  • An exercise program that has aerobic and weight-training elements can help you to lose weight and build muscle mass.
  • Stress reduction and sleep toiletry can help you to manage emotional eating and support quality sleep.
  • Vitamin D supplementation may also play a role in reducing the risk of developing prediabetes, though more research is indicated.
  • Stop smoking.
  • In some cases a doctor may want to use a drug like metformin, short term, especially if you are considered high risk for progressing to diabetes.

Learning that you have insulin resistance can be an early wake up call to modify your lifestyle, so you reverse insulin resistance and hyperglycemia. That means you preempt a diagnosis of prediabetes and diabetes long before they strike.  You hold the power to literally reverse this disease process before serious damage and disease occur.

See more helpful articles:

8 Myths About Insulin

A Beginner's Guide to Taking Insulin

What to Ask Your Doctor About Insulin

Sources:

National Institute of Diabetes and Digestive and Kidney Diseases

National Heart, Lung and Blood Institute

Joslin Diabetes Center