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What Is Insulin Resistance And Why Should I Care About It?

Published:
Feb 12, 2021
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Updated:
Jun 4, 2021
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Contributor:
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11 minutes

Medically reviewed by

Ford Brewer, MD, MPH
Ford Brewer, MD, MPHFord Brewer, MD, MPH
Head of Prevention at PrevMed
Dr. Brewer is a board-certified preventative & occupational medicine specialist. Dr Brewer is also a globally recognized speaker and thought leader particularly for heart attack, diabetes, prediabetes & stroke prevention.
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Wondering about insulin resistance? You’ve come to the right place. I’m a preventive medicine doctor who has dedicated my career to tackling the top causes of disease and death. I spend a lot of time educating my patients and the general public on insulin resistance, which I see as the number one driver behind poor health in the world. I hope this article helps you on your path to optimal health.


What is insulin resistance?

Before I describe insulin resistance, allow me to share a simple high school biology refresher. When you eat, your digestive system breaks down sugar and deposits it into your bloodstream. Then, the higher blood sugar concentration triggers the pancreas to produce a hormone called insulin. The insulin binds to insulin receptors in the cell membrane, which creates an opening that sugars can pass through. Then, the sugars can provide the cell with needed energy. See? Simple.

Insulin resistance occurs when the insulin receptors stop functioning properly. When this happens, the receptors need more insulin to create a pathway for sugars to enter the cells. As insulin resistance progresses, the pancreas is no longer able to produce enough insulin to bring enough sugars into the cells. This can lead to low energy. Meanwhile, you end up with too much sugar in your blood, which leads to a range of serious health problems.

Over time, insulin resistance progresses to the point where it is labelled as diabetes.

This all sounds scary, and it is. But the good news is it’s possible to stop insulin resistance from getting worse and even reverse it.

 

What causes insulin resistance?

Insulin resistance happens for a number of reasons. Age and obesity are the biggest factors, but genetics and lifestyle are also key contributors.  

  • Age – Insulin resistance is much more common after age 45. It is especially important to test your glucose and insulin levels and pay attention to diet as you get older.
  • Genetics – People who are of African-American, Hispanic, Indian, and Native American descent are at a higher risk of insulin resistance. Those who have diabetes in their families are also more likely to develop insulin resistance.
  • Stress – Chronic stress over time can contribute to insulin resistance. Stress hormones cause the liver to release sugar into the blood, contributes to the blood sugar and insulin spikes that wear out the insulin receptors.
  • Sleep – Poor sleep, over a long period of time, can be one factor contributing to insulin resistance. One reason is that sleep deprivation leads to high production of the stress hormone cortisol, which, as mentioned above, triggers the liver to release stored sugars. In future posts, I’ll talk more about the relationships between sleep, stress and insulin resistance.
  • A very high-sugar or high-carb in the diet – Repeated sugar spikes means your insulin receptors have to work overtime, and they can get worn out.
  • Body-mass indexes (BMIs) considered obese or overweight  – Your fat cells produce cytokines, or proteins. Too much of these cytokines will interfere with the healthy functioning of your insulin receptors. The fat cells stored around the organs in the belly are especially prone to producing harmful cytokines. In other words, excess belly fat drives insulin resistance. 

I’d like to reiterate here that insulin resistance will not inevitably cause serious damage or lead to diabetes. Some people will develop insulin resistance no matter how healthy they are, due to age and genetics. But if they remain at a healthy BMI and lower their carb intake, they can ensure their insulin resistance doesn’t  get to a danger level. They can avoid severe insulin resistance, which leads to heart disease, vision loss, and other health issues. The first step is knowing if you have insulin resistance.

Similarly, if you are overweight, you can stop insulin resistance from progressing and even reverse it by losing weight and reducing your carb intake.

 

How do I know if I'm insulin resistant?

Here’s the problem. Most people who have insulin resistance don’t know they have it.

One third of Americans have insulin resistance, according to the Centers for Disease Control (CDC). But four out of five people who have insulin resistance don’t know they have it. While insulin resistance may cause symptoms in the early stages, such as low energy, many people will not notice symptoms. But that doesn’t mean insulin resistance isn’t causing damage in the body. The only way to know if you have insulin resistance is to test for it.


Why should I be concerned about insulin resistance?          

Consider insulin resistance as an alarm bell you can’t afford to ignore. If you have insulin resistance, or low insulin sensitivity, it means you’re at an increased risk for the following:

  • heart attack
  • stroke
  • vision loss
  • erectile dysfunction
  • kidney disease
  • dementia

 

How can insulin resistance cause all these widespread problems? 

The answer lies in the arteries, which are found throughout your body, especially in the organs. Over time, high amounts of sugar and insulin in the blood damage the lining of our arteries. The damage weakens the arterial lining and makes it easier for cholesterol molecules to enter through the artery wall. This cholesterol builds up inside the artery as plaque. This narrows the opening in the artery. When the immune system attacks the plaque and liquifies it, this liquid plaque can squirt into the artery, causing a clot. As we know, clots can result in heart problems and stroke.

Meanwhile, our white blood cells in our immune system attacks these plaques, producing inflammation in the body – what medical folks call a liquid ‘hot’ plaque. It doesn’t sound good, and it’s not. This immune response can lead to blood clots. A narrowed artery and increased clots are the perfect recipe for heart disease and strokes. 

We used to think that eating eggs and other foods with cholesterol caused heart attacks and strokes. We now know that insulin resistance and excess insulin and sugar in the blood is a far bigger culprit.

The same arterial damage that leads to heart attack and stroke can lead to a number of other problems. Insulin resistance can lead to damaged arteries in the eye, causing vision loss. And high insulin and sugars in the blood can erode artery walls in the kidneys and genitals, causing kidney disease and erectile dysfunction.

 

The damage happens even before diabetes is officially diagnosed

Many people think that insulin resistance is only a problem when it’s progressed to diabetes. This isn’t true. Studies show that 15% to 20% % of people already have damage to their retina by the time they’re diagnosed with diabetes. In other words, the damage occurred when they had prediabetes. Studies show that people with prediabetes have a 20% increased chance of stroke and a 15% increased risk of heart disease. This is serious. Heart disease is the number one cause of death in America. Strokes are a leading cause of disability.


Remember, once plaques build up in the arteries, they don’t have to completely close the arteries to cause a problem. Many people with prediabetes, or insulin resistance, will perform fine on a stress test, because their arteries are only slightly occluded with plaque. But it only takes a bit of bad luck for that hot liquid plaque to break through the lining of the artery and cause a clot. Tim Russert, the famous TV host of Meet the Press had a normal stress test result just over a month before his tragic heart attack death in 2014.

As I tell my patients, the goal should be to reverse insulin resistance as much as you possibly can.

 

How can I reverse insulin resistance - what are the most effective lifestyle changes?

Here’s the part you’ve been waiting for. Yes, it’s possible to reduce insulin resistance, even to the point where you no longer have insulin resistance. Research shows that with the right diet, insulin receptors start to work better within just a couple of months.


The best way to stop insulin resistance is to lose fat. 

This way, you’ll lower the amount of cytokines (released by fat cells) that damage the insulin receptors. You can lose weight in a number of ways, by eating fewer calories; by intermittent fasting; by eating more nutrient-dense and fiber-rich calories, such as vegetables, legumes, lean meats and fish and whole grains. About half the patients I work with are able to improve their body’s insulin response over time by losing weight. Others don’t entirely reverse their insulin resistance with weight loss but because of their weight loss, their blood sugar levels stop increasing. In other words, their pre-diabetes never progresses to diabetes.


You especially want to reduce your carbohydrates and sugars. 

This will not only help you lose weight, it will also reduce the pressure on your pancreas to produce insulin. And the less sugar you consume, the less potential for damage to your arteries.


Getting enough sleep and reducing your stress levels are also vital.

Both poor sleep and stress contribute to the development of insulin resistance by triggering the liver to release sugars into the bloodstream. 


Exercise is a great way to increase insulin sensitivity and lower insulin resistance.

When we exercise, especially moderately or vigorously, our body triggers our muscles to take up more glucose. This occurs even during exercise recovery. In other words, this continues for many hours after exercise. This means the pancreas doesn’t have to overproduce insulin to process blood sugar. In other words, exercise contributes both to healthier blood sugar and blood insulin levels. 


In future posts, I’ll go into more detail about the roles that sleep, exercise and stress play in the development of insulin resistance. I’ll also talk more about low-carb diets, and whether certain vitamins can help to reduce insulin resistance.

 

Tests to measure insulin resistance

Fasting Glucose Test: 

This blood test measures the level of sugar in your blood after you haven’t consumed calories for eight hours. A number of 99mg/dL or below is considered normal. Numbers 100 to 125 typically mean someone is insulin resistant, but hasn’t yet developed full blown diabetes. And numbers above 126 mean diabetes.

 

Oral Glucose Tolerance Test:

This is a blood test to see how your body processes sugar. You start with a fasting glucose test, and then you take a drink with exactly 75mg of sugar. (That’s the equivalent of a large-size coke at a fast-food restaurant). Two hours after that, you take another blood test.

At this two-hour mark, 139mg/dL or below is considered normal. (Anything below 120mg/dL is ideal). But 140 to 199 means your body isn’t processing sugar as fast as it should, indicating insulin resistance. If you’re at 200 or above, that’s considered diabetes.

If your results are borderline, a doctor often recommends a three-hour OGTT, where you take a 100mg sugar drink and test the blood after one, two, three hours. This gives a more detailed picture.

 

4-hour Kraft Insulin Survey: 

This is the gold-standard test for insulin resistance, though it is rarely done. This test measures not only the amount of glucose with a glucose tolerance test. It also measures the amount of insulin in your blood. Between two and three hours after consuming 100mg of glucose, insulin levels below 60 mIU/L are normal, while anything between 60 and 99 is borderline, and a result above 100 is considered insulin resistance.

I recommend this test as it not only shows how quickly you process sugar, it also shows how much insulin you need to produce in order to clear sugar from your bloodstream.

 

Why a fasting glucose test isn’t enough

Most people who are insulin resistant – a whopping 90% – don’t realize it. That’s because most doctors don’t routinely check glucose levels, and if they do, they only test fasting glucose, which doesn’t show the full picture.

As a doctor with insulin resistance myself, and as someone who has helped hundreds of patients lower their blood glucose and insulin levels, I recommend doing a fasting glucose test, an oral glucose tolerance test, and an insulin test.

Let me share an example to illustrate my point. A patient of mine was concerned about diabetes. Why? He was slightly overweight, he had family members with diabetes, and his father had died of a heart attack. He told me his family doctor checked his fasting glucose once a year and it always came back normal.

So I ran the tests. His fasting glucose indeed came back normal, at 88mg/DL. But when we did an oral glucose tolerance test, his sugar levels were through the roof: at 291mg/Dl at the two-hour mark. (Remember, anything above 200 is diabetes). As you can see, fasting glucose doesn’t tell the whole story. Some people can bring their sugars down to normal levels over time (and therefore have a normal fasting glucose) but the worrying part is that it takes them too long to do so. The sugar in their bloodstream can still cause damage. This is especially common in prediabetes and early diabetes.

 

The importance of testing insulin, not just blood sugar 

Not only do I recommend an oral glucose tolerance test, I also recommend getting your insulin levels checked.

I’ll give you an example with another patient here. Her glucose tolerance test came back fine. Her blood sugars were 124mg/dL after two hours. But her insulin was alarmingly high, at 290 mIU/L.

Why does this happen? When our insulin receptors become less efficient, our body responds by producing more insulin. For a while, this strategy works. The extra insulin is able to quickly remove the sugars from our bloodstream through the insulin receptors, even if those receptors aren’t functioning that well. You can imagine the extra insulin supercharging sugars to kick through rusty doors to our cells. But over time, our pancreas wears out from having to produce extra insulin, and it can’t keep up. When this happens, people end up with too much sugar in the blood, AKA, diabetes.


Raising awareness to save lives

It’s my mission to stop people from progressing to diabetes, and to help people lower their level of insulin resistance. That’s why I want to help people find out about insulin resistance at the beginning stages. In the early stages of insulin resistance, or in pre-diabetes, it’s possible that glucose tests will be normal but insulin tests are not normal.

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