Insulin resistance (IR)[1] is a condition characterized by the body’s cells becoming unresponsive to the effect of insulin[2] (a hormone that helps move glucose from the blood into the cells for energy). This can lead to high blood glucose (known as hyperglycemia[3]) and typically results in higher insulin secretion by the pancreas and higher-than-normal levels of insulin in the blood (hyperinsulinemia).
You may already know that insulin resistance is a hallmark of prediabetes[4] (a condition in which blood glucose levels are high but not high enough to be considered diabetes). It is estimated that more than 96 million American adults[5] — one in three — have this condition. And more than 80% of them don’t know they have it. It is generally associated with a number of factors, including a lack of physical activity[6], an unhealthy diet[7], smoking[8], overweight or obesity[9] with excess fat around the abdomen, and a family history of type 2[10] or gestational diabetes[11].
If it progresses, prediabetes can develop into type 2 diabetes. But did you know that insulin resistance is a factor in a number of health challenges besides just prediabetes and type 2 diabetes? In this article, you will learn how insulin resistance can influence certain additional conditions and discover that there are extra benefits to managing your blood glucose beyond just diabetes.
Let’s make one thing clear before we start: The objective is not zero insulin. Insulin is a vital hormone, and your body cannot function without it. We mainly know it for its primary role of facilitating the entry of glucose into cells. But insulin is a multitasker (see “Some of the Many Functions of Insulin”). And at the right level, it’s very beneficial. But just like a lot of good things, too much of it can be a bad thing. So, without further ado, let’s look at the first condition associated with insulin resistance.
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Dementia is a general term that describes a decline in memory and other cognitive skills. Alzheimer’s disease (AD)[13] is the most common form of dementia. According to the Alzheimer’s Association, more than 6 million Americans live with Alzheimer’s disease[14]. The condition has many risk factors, including advancing age and genetics. But as of today, there’s not much that can be done about those. So, let’s focus on what appears to be a modifiable risk factor for this condition: According to some researchers, reducing insulin resistance may decrease the risk of susceptibility to Alzheimer’s. There is such a strong link between the two conditions, in fact, that Alzheimer’s is sometimes called “type 3 diabetes.”[15]
What is insulin’s role here? After the hormone has done its job, it needs to be taken out of the bloodstream. Otherwise, your blood sugar plummets, and you develop low blood sugar (hypoglycemia)[16]. Removing insulin from the bloodstream is the responsibility of an aptly named enzyme: Insulin-degrading enzyme (IDE). IDE is a multitasking enzyme. It also helps dissolve amyloid plaque, gooey clumps of protein that can accumulate in the brain and have been linked to Alzheimer’s. One possible (simplified) explanation: If IDE is constantly busy with insulin, it cannot do a good job of removing the amyloid plaque, and it is allowed to build up in the brain.
Insulin resistance also deprives the brain’s cells of the fuel they need to function properly. Additionally, over time, the increased blood glucose levels caused by insulin resistance can damage blood vessels, including those in the brain.
While the right level of insulin has a positive effect on the brain (see “Some of the Many Functions of Insulin”), research suggests that “insulin resistance may damage the cognitive system and lead to dementia states.[17]” Researchers followed a group of 3,695 participants, ages 30 to 86, for 11 years. They found that HbA1c (also known as A1C[18], a measure of long-term glucose control) levels were linked with cognitive performance: higher HbA1c results equaled lower cognitive performance.
Lifestyle modifications may have an impact. A number of researchers suggest that intermittent fasting, by, for example, limiting calorie intake to a 12-hour period during the day (with the approval of your doctor), is a way to improve insulin sensitivity and may help with slowing cognitive decline. Although studies into this approach are preliminary, there is evidence that certain types of intermittent fasting can help delay the onset and progression in models of Alzheimer’s in animals. (Learn more about intermittent fasting and diabetes[19].)
This was our first example. Next, we will look at another common condition that can be associated with insulin resistance.
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Regulating blood glucose by facilitating the movement of glucose from the bloodstream into the cells
Modifying the activity of enzymes (proteins that help speed up metabolism)
Managing the creation of lipids by uptake into fat cells
Managing breakdown of protein and lipids
Allowing for the uptake of amino acids (the building blocks of proteins) and potassium[20] into the cells
Building muscle following sickness or injury by facilitating the uptake of amino acids
Managing the excretion of sodium and fluid volume in the urine
Improving the memory and learning capabilities of the brain
(Source: news-medical.net[21])
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Blood pressure[22] is a combination of heart rate[23], how much blood the heart pumps out, and the resistance in the arteries. If one of those factors increases, and the other ones are stable, blood pressure will go up. It is normal for blood pressure to go up and down during the day, but it becomes problematic when it stays up.
High blood pressure (hypertension)[24] is defined as a systolic blood pressure (top number) over 130 mmHg or a diastolic blood pressure (bottom number) greater than 80 mmHg. According to the U.S. Centers for Disease Control and Prevention (CDC), nearly half of adults in the United States live with hypertension[25]. And, sadly, only 24% of them have the condition under control. There are two main types of hypertension: primary and secondary. Primary, also called essential, high blood pressure represents roughly 90-95% of the cases, and in these cases, the cause is unknown. Secondary high blood pressure is caused by a known medical condition.
So, how does insulin resistance fit in the picture? It has to do with insulin’s effect at the kidney level. One of the ways that the high insulin levels characteristic of insulin resistance raise blood pressure is by decreasing sodium excretion by the kidneys. This retained sodium (and the water it pulls into the bloodstream) puts more pressure on blood vessels, thus increasing the resistance from the blood vessels. In this case, a doctor may prescribe a diuretic in order to flush out the excess water.
On a separate front, insulin resistance is linked with a loss of magnesium (Mg)[26], a mineral that helps blood vessels relax, in the urine. When magnesium is low, blood vessels cannot relax as well, and the ensuing constriction can chronically raise blood pressure. Some research has concluded that magnesium supplementation can help lower blood pressure in people with insulin resistance.
Now you are getting to know some new angles to insulin resistance. We’ve covered two situations where chronic high levels of insulin in the blood can cause health problems. We now move on to our third example, and this one is a double whammy: It combines the effects of high insulin levels and high blood glucose levels.
We all have defective cells in our bodies. They develop for a variety of different reasons, such as unhealthy diet, exposure to toxins, chemical substances, chronic stress, and so forth. Under normal conditions, your body can manage those cells and keep them in check. But left unchecked, they can grow uncontrollably, a condition known as cancer. In 2020, the five most common cancers[27] in the United States were breast, prostate[28], lung, colorectal[29], and melanoma[30]. It is estimated that close to 40% of the population will get a cancer diagnosis at some point.
Let’s first look at hyperinsulinemia: Insulin is considered an anabolic agent, or a substance that stimulates the growth or creation of body tissues. In studies, hyperinsulinemia has been associated with cancer mortality independently of diabetes, obesity, and metabolic syndrome. In some research, people with hyperinsulinemia also have been found to have an increased risk[31] of breast, colorectal, prostate, pancreatic, endometrial, liver, and ovarian cancers.
Now, onto the hyperglycemia aspect: Glucose is the preferred energy source for cancer cells. Studies have shown that hyperglycemia “raises the prevalence of[32] and mortality from certain cancers,” such as breast, liver, bladder, pancreatic, colorectal, and endometrial cancers.
So, now you know a bit more about insulin resistance and the importance of managing your blood glucose. The explanations of these processes were simplistic — metabolic diseases are complex, with many causes, and they take years to develop — but the takeaway is this: When you get a warning sign, take it seriously. Make the necessary adjustments. It’s never too early to prevent a disease from developing.
Educate yourself, and take action. Bear in mind that we all have different lives and physiology, so what works for one person may not work for another. But give your body what it needs, and it will adjust the course. (Learn about lifestyle hacks for managing blood sugar[33].) Have a conversation with your doctor about your objectives and what changes you are making to improve your health and avoid insulin resistance. A safe and gradual approach is best.
Want to learn more about insulin resistance? Read “Insulin Resistance: Your Questions Answered”[34] and “Insulin Resistance: What You Need to Know.”[35]
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