What you need to Know About Insulin Resistance

Insulin resistance occurs when cells in your muscles, body fat, and liver start ignoring instructions from the hormone insulin to ferry sugar out of the bloodstream.

One in three Americans—including half of those 60 and older—has a silent blood sugar problem known as insulin resistance. Insulin resistance increases the risk for prediabetes, type 2 diabetes, and a host of other serious health problems, including heart attacks, strokes, and cancer.

What Is Insulin Resistance?

Insulin resistance occurs when cells in your muscles, body fat, and liver start resisting or ignoring the signal that the hormone insulin is trying to send out—which is to grab glucose out of the bloodstream and put it into our cells. Glucose, also known as blood sugar, is the body’s main source of fuel. We get glucose from grains, fruit, vegetables, dairy products, and drinks that break down into carbohydrates.

When your cells don’t respond adequately to insulin’s signal, it results in too much glucose remaining in your bloodstream (high blood sugar). This can lead to prediabetes, which in turn can progress into full-blown type 2 diabetes.

How Insulin Resistance Leads to Diabetes

As insulin resistance develops, your body fights back by producing more insulin. Over months and years, the beta cells in your pancreas that are working so hard to make insulin get worn out and can no longer keep pace with the demand for more and more insulin. Then—years after insulin resistance silently began—your blood sugar may begin to rise and you may develop prediabetes or type 2 diabetes. You may also develop non-alcoholic fatty liver disease (NAFLD), a growing problem associated with insulin resistance that boosts your risk for liver damage and heart disease.

Signs and Symptoms of Insulin Resistance

Insulin resistance is usually triggered by a combination of factors including body weight, age, genetics, ethnicity, being sedentary, smoking, and possibly even skimping on sleep. Specific signs that may indicate that you have or are likely to develop insulin resistance include:

A Large Waist

Experts say the best way to tell whether you’re at risk for insulin resistance involves a tape measure and moment of truth in front of the bathroom mirror. A waist that measures 35 inches or more for women, 40 or more for men (31.5 inches for women and 35.5 inches for men if you’re of Southeast Asian, Chinese or Japanese descent) increases the odds of insulin resistance and metabolic syndrome, which is also linked to insulin resistance.

Dark Skin Patches

If insulin resistance is severe, you may have visible skin changes. These include patches of darkened skin on the back of your neck or on your elbows, knees, knuckles or armpits. This discoloration is called acanthosis nigricans.

Other important Signs of Metabolic Syndrome

According to the National Institutes of Health, in addition to excess abdominal fat (as measured by waist circumference), if you have two or more of the following (or any three of the following without a large waist circumference), you likely have metabolic syndrome, which creates insulin resistance:

High triglycerides. Levels of 150 or higher, or taking medication to treat high levels of these blood fats.

Low HDL (“good”) cholesterol. High-density lipoprotein levels below 50 for women and 40 for men, or taking medication to raise HDL levels.

High blood pressure. Readings of 130/85 mmHg or higher, or taking medication to control high blood pressure.

High fasting blood sugar. Levels of 100 to 125 mg/dl (the prediabetes range) or over 125 (diabetes), or taking medication to treat high blood sugar.

Insulin Resistance Risk Factors

Understanding the risk factors for insulin resistance can help prevent, delay, or lessen unhealthy outcomes. If you’re aware of what to watch out for, you can sometimes modify or even eliminate some of the factors associated with lifestyle habits. Insulin resistance risk factors include:

Being 45 or older
Having a high BMI
Having a parent or sibling with diabetes
Having a sedentary lifestyle
A personal history of gestational diabetes
A personal history of heart disease or stroke
Medical conditions such as high blood pressure and high cholesterol
Polycystic ovary syndrome (PCOS)
Cushing’s syndrome
Sleep apnea and other problems with getting enough sleep

Complications of Insulin Resistance

An estimated 87 million American adults have prediabetes; 30% to 50% will go on to develop full-blown type 2 diabetes. If unmanaged, insulin resistance can lead to type 2 diabetes.

In addition, up to 80% of people with type 2 diabetes have NAFLD. But those aren’t the only threats posed by insulin resist

Thanks to years of high insulin levels followed by an onslaught of cell-damaging high blood sugar, people with insulin resistance, prediabetes, and type 2 diabetes are at high risk for cardiovascular disease.

Insulin resistance doubles your risk for heart attack and stroke—and triples the odds that your heart attack or "brain attack" will be deadly, according to the International Diabetes Federation. In a large study of over 28,000 women, researchers at Brigham and Women’s Hospital in Boston found that insulin resistance was a strong predictor of cardiovascular disease.

Meanwhile, insulin resistance and metabolic syndrome are also linked with higher risk for cancers of the bladder, breast, colon, cervix, pancreas, prostate and uterus. The connection: High insulin levels early in insulin resistance seem to fuel the growth of tumors and to suppress the body’s ability to protect itself by killing off malignant cells.

Research has also found a strong association between insulin resistance and memory function decline, increasing the risk for Alzheimer’s disease.

Insulin resistance is also a problem if you have already been diagnosed with type 1 or type 2 diabetes. Higher levels of insulin resistance make the condition more challenging to manage. You might need to take a higher dose of diabetes medication in order to achieve your target blood sugar levels.

Diagnosing Insulin Resistance

Health care providers don’t usually test people for insulin resistance but it is something you can request of your doctor when they do your blood tests.

Instead, health care providers look for prediabetes using blood tests that measure the level of sugar (glucose) in your bloodstream. The two most common tests are a standard fasting blood glucose test and an A1c (also called hbA1c) blood test, which measures the average amount of glucose in your bloodstream over a period of three months.

Fasting Plasma Glucose Test

The fasting plasma glucose test reveals your blood sugar level at the time of the test. Fasting is defined as not having anything to eat or drink (except water) for eight to 12 hours before the test. The test is typically performed in the morning, before you eat breakfast. A test result of 100 to 125 mg/dL (milligrams per deciliter) might indicate that you have impaired insulin sensitivity.

A1c Test

The A1c test is a simple blood test. Because the results reflect your average blood sugar levels over the preceding three months, it doesn’t have to be performed fasted. An A1c level below 5.7% is considered normal, while levels between 5.7% and 6.4% suggest that your cells are not as sensitive to insulin as they should be, and suggests prediabetes. A level higher than 6.5% is considered diabetes.

How You Can Prevent or Reverse Insulin Resistance

Losing weight, getting regular exercise, and not skimping on sleep can all help improve your insulin sensitivity. Don’t rely on dieting or exercise alone: In one University of New Mexico School of Medicine study, published in the International Journal of Obesity, overweight people who lost 10% of their weight through diet plus exercise saw insulin sensitivity improve by 80%. Those who lost the same amount of weight through diet alone got a 38% increase. And those who simply got more exercise, but didn’t lose much weight, saw almost no shift in their level of insulin resistance.

There are many effective actions you can take and healthy habits you can foster to prevent insulin resistance. These interventions may even help reverse insulin resistance. They include:

Eating fewer processed foods (bagged and boxed)
Moving around more during the day
Participating in any form of activity you will be able to do regularly
Ensuring you get enough high-quality sleep
Taking steps to actively reduce stress
Asking for support from family, friends, and health care providers
Making a plan to help you reach your food and exercise goals

For some people, weight loss may also help. An NIH-funded study found that for people at high risk of developing diabetes, losing just 5% to 7% of their starting weight helped them delay or even prevent a diabetes diagnosis. The same study also showed that for younger adults, people with obesity, and those with a history of gestational diabetes, the medication metformin (Glucophage)—used to treat those who already have diabetes—can also delay the onset of diabetes.

Foods to Avoid If You Are Insulin Resistant

Foods with added fats should be avoided or enjoyed in smaller portions. These include trans fats, which are primarily found in hydrogenated vegetable oils like margarine and shortening.

Try to reduce or eliminate your consumption of foods with added sugars, such as sweetened drinks, candy, or high-sugar breakfast cereals.

Cut down on refined grain products that are high in fast-absorbing carbohydrates but low in fiber. Examples include white bread, white potatoes, white rice, and pasta that isn’t whole-grain.

When purchasing or consuming food products, check the nutrition labels for total carbohydrates and sugar content. Decreasing your carbohydrate, sugar, and trans fat intake while eating more nutritious alternatives can help to lower your blood sugar. In turn, this will lessen or even prevent insulin resistance.