What Is Insulin Resistance?

blood glucose blood tests carbohydrates diabetes elimination diet fasting insulin test fasting plasma glucose test fatty acids fatty liver fructose glycemic index glycogen hba1c test high-fructose corn syrup homa-ir hormonal disorders insulin insulin resistance insulin sensitivity lifestyle changes liver cells medications oral glucose tolerance test pancreas physical activity prediabetes skeletal muscles white fat cells Mar 09, 2024

A stethoscope, a bottle of pills, and a glucometer

At least 1 in 3 American adults has insulin resistance — and often, they don’t know it.¹

Insulin resistance wreaks havoc on your health long before it’s diagnosed. It harms your brain, your eyes, your heart, your kidneys, and your other organs. And if that’s not bad enough, having insulin resistance can worsen just about any other health condition you may be dealing with.²

In this article, we’ll talk about key aspects of this modern plague:

What is insulin?
Insulin sensitivity vs. resistance
What causes insulin resistance?
How can you find out if you have insulin resistance?
Can insulin resistance be reversed?

Let’s start off by seeing just what insulin is, and how it works.

What is insulin?

Insulin is a protein hormone made by the beta cells of your pancreas. This hormone controls your levels of glucose (blood sugar), which comes from the foods you eat.³

Most people have heard of the primary function of insulin, which is to alert your cells to take up glucose from your bloodstream. Insulin also regulates the breakdown of carbohydrates, lipids, and proteins in your body. It helps your cells divide and grow too.³

Insulin works mainly on your skeletal muscle, white fat, and liver cells. It helps your skeletal muscle use glucose for energy, or to store it for later as glycogen. Meanwhile, insulin suppresses the breakdown of fat in your white fat cells. Lastly, insulin promotes glucose storage in your liver.⁴

Your blood sugar levels fall once glucose enters your cells. In response to this drop, your blood insulin levels should decrease as well. Lower insulin levels signal your liver to release glycogen and turn it back into glucose. When this process works well, you’ll have energy all the time even if you haven’t eaten for a while.⁵

Insulin sensitivity vs. resistance

Insulin sensitivity describes how responsive your body is to the effects of insulin. If you’re insulin sensitive, smaller amounts of insulin are effective to reduce your blood glucose levels.⁶

Sometimes, your muscle, fat, and liver cells don’t seem to respond properly to insulin. Through a variety of mechanisms, their ability to absorb or store glucose becomes impaired. This condition is called insulin resistance.^5,7

Insulin resistance is the opposite of insulin sensitivity. If you’re insulin resistant, you have low insulin sensitivity.⁸

This lower response has two implications. First, your pancreas will try to produce more insulin in an attempt to force your cells to accept more glucose. As a result, you’ll have high levels of insulin in your blood, but your blood sugar will stay within the normal range.⁷

This situation is unsustainable though. Over time, as the demand for insulin exceeds your pancreas’ ability to produce it, you’ll wind up with high blood sugar levels too. Eventually, these raised blood sugar levels lead to the diagnosis of prediabetes and type-2 diabetes (T2D).⁷

What causes insulin resistance?

Genetic, hormonal, and lifestyle factors can lead to insulin resistance.⁹

Some people are born with insulin resistance syndromes. These rare conditions arise from defects in genes responsible for insulin signaling. The mildest one is called Type A insulin resistance syndrome. This condition hampers blood sugar control, resulting in diabetes. Insulin resistance and other symptoms appear in puberty or later. But the syndrome isn’t life-threatening in general.⁹

Rabson-Mendenhall syndrome and Donohue syndrome are more serious conditions. People with these genetic diseases are unusually small even before birth. As infants, they fail to grow and gain weight at the expected rate. They develop insulin resistance early in life too. People with Rabson-Mendenhall syndrome usually live only until their teenage years or maybe their 20s. Typically, they die from diabetes-related complications. Meanwhile, most children with Donohue syndrome don’t live beyond the age of 2.⁹

Disorders involving other hormones can also cause insulin resistance in different ways. For instance, Cushing’s syndrome happens when your body produces excess cortisol. Cortisol is often called the stress hormone, and too much of it can counter the effects of insulin.⁹

Acromegaly is another hormonal disorder involving high levels of growth hormone (GH). Elevated GH can increase glucose production, which can then lead to insulin resistance.⁹

There’s hypothyroidism as well. This complex condition arises when you don’t have enough thyroid hormone. As a result, your body takes a long time to break down glucose. The slower clearance time can lead to insulin resistance.⁹

For many people though, lifestyle factors play a major role in developing insulin resistance. Most often, it’s regularly consuming too many sugary and starchy foods that leads to rapid increases in insulin production. The overdrive makes your muscle, fat, and liver cells less responsive to insulin over time. Eating too much sugar can also increase free fatty acids in your blood. Higher levels of free fatty acids further hinder your cells from responding well to insulin.^9,10

Being physically inactive can cause insulin resistance too. It prevents you from building and maintaining muscle mass that can absorb glucose from your blood. Plus, physical inactivity can lead to weight gain, which is associated with insulin resistance.⁹

Lastly, some medications can cause insulin resistance. These include steroids and drugs that are prescribed for controlling blood pressure, as well as those for treating HIV and psychiatric illnesses.⁹

How can you find out if you have insulin resistance?

Insulin resistance doesn’t have any of its own symptoms. Typically, you won’t know you’re insulin resistant until after you start showing symptoms of high blood sugar. These include feeling unusually hungry or thirsty. You may notice you need to pee more often. You may get headaches, or your vision may get blurry. You may get skin infections, and cuts and sores may heal more slowly.⁹

As insulin resistance progresses to prediabetes, the skin in your armpits, your back, or on the sides of your neck may get dark. You may get skin tags or begin to have problems with your eyes.⁹

Although there’s no direct test for insulin resistance, there are a couple of tests that can measure your insulin levels.

If your blood sugar levels are normal, the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) test can estimate how resistant your cells are to insulin, based on your blood glucose and insulin levels after fasting for at least 8 hours.¹¹

Another readily available but infrequently performed test is the fasting insulin test. This test measures the amount of insulin in your blood after 8 to 12 hours of fasting. You may have insulin resistance if your fasting insulin is high.¹²

More commonly, your doctor will diagnose insulin resistance indirectly using one of the three main blood tests for diagnosing prediabetes or T2D. If you have either of these conditions, then you have insulin resistance as well.

First is the fasting plasma glucose (FPG) test, which measures your blood sugar 8 to 12 hours after you haven’t eaten or drunk anything.¹³

Second is the oral glucose tolerance (OGT) test. This test measures how well your body can process a higher amount of sugar. For your OGT, you’ll have to take the FPG test, then drink a sugary solution. Your blood sugar will then be measured again after two hours.¹³

The third test is the hemoglobin A1c (HbA1c) test. This exam measures your average blood sugar level for the past three months.¹³

Can insulin resistance be reversed?

If you suspect you may have insulin resistance, here’s some good news: the condition is reversible. The key is to make changes in your lifestyle right away.⁹

Your diet has a major impact on your blood glucose and insulin levels. Your body will need more insulin to break down foods that are highly processed, or that contain a lot of simple carbohydrates like sugars and starches.⁹

You can use the glycemic index (GI) to choose which foods to eat and which ones to avoid. The GI ranks carb-containing foods from 0 to 100 based on how much they affect your blood sugar. In general, low-GI foods — those with a GI of 55 or less — are low in simple carbs. In contrast, they’re high in fiber, which takes longer for your body to digest. Thus, low-GI foods are helpful for controlling your blood sugar levels.⁹

As for foods to avoid, those with fructose deserve special mention. Fructose, a simple sugar found in fruits, is also the main component of high-fructose corn syrup (HFCS). HFCS is a cheap, highly processed sweetener used to prolong the shelf life of pre-packaged foods. Candies, cookies, cereals, crackers, breads, jams, sauces, ice cream, and fast food all contain HFCS. So do drinks like soda, sweetened teas, and even some juice products.^8,14

Your liver cells process most of the fructose that enters your body. In your liver, fructose is broken down into glucose and glycogen. But your liver can store glycogen only in limited amounts. Once your liver has reached its glycogen storage capacity, any excess fructose turns into liver fat. A fatty liver is a direct cause of insulin resistance. So, to reverse insulin resistance, you’ll want to stay away from foods with fructose — even fruits, but especially HFCS.^14,15,16

Conclusion

If you have insulin resistance, you may or may not experience symptoms. Some blood tests can help diagnose if you have this condition, but the most common indicator is high blood sugar levels — and most likely, prediabetes and T2D later on.

Although genes, hormones, and lifestyle can all contribute to insulin resistance, it’s possible to reverse insulin resistance through lifestyle changes.

The main thing you can do is modify your diet. It’s especially important to avoid fructose, since overconsumption of this simple sugar can lead directly to insulin resistance.

Need help getting started? Get all the guidance and structure you need with the Diabetes Diet Solution.

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