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Insulin and insulin resistance

What is insulin, and what does it do? What is insulin resistance? What are the symptoms of insulin resistance? What causes it, and how to deal with it?

What is insulin?

Insulin is a hormone produced by our pancreas.

Insulin ensures that glucose (sugar) in the blood enters the body’s cells, thus providing them with energy.

Insulin also affects fat and protein metabolism – it helps break down fat or protein for energy.

Respectively – insulin regulates the sugar level in our blood – if the glucose (sugar) level in the blood increases, the pancreas produces more insulin so that the cells can absorb more glucose and the amount of glucose in the blood balances out.

If the insulin level is too low, or the body’s cells do not respond to insulin as effectively as they should (insulin resistance), the blood sugar level rises.

A slight increase in blood sugar is usually not a cause for concern, since it can be treated relatively easily or it returns to normal on its own. However, hyperglycemia can be potentially dangerous if blood sugar levels remain high for a long time or become very high.

Very high blood sugar levels can cause life-threatening complications, such as:


What is insulin resistance?

Insulin resistance is a very common condition, but its prevalence among adults varies from country to country, ranging from about 15.5% in Europe to about 46.5% in Venezuela.

Insulin resistance (also known as reduced insulin sensitivity) is a condition in which cells in the body (muscle, fat, liver, etc.) do not respond to insulin as they should.

It is a very complicated process, and under normal conditions, it works as follows:

  1. Carbohydrates are broken down into simple sugars in the digestive tract.
  2. Sugar enters our bloodstream, the blood sugar level rises and the pancreas is “commanded” to release insulin.
  3. Insulin helps sugar from the blood enter the cells of the body, where it is used for energy.
  4. Insulin also signals the liver to store blood sugar for later use.
  5. The blood sugar level gradually decreases, and the pancreas is “commanded” to reduce the release of insulin.
  6. Lower insulin levels signal the liver to release stored sugar – blood sugar levels rise, and cells have energy again, even if you haven’t eaten for a while.

However, this very complex system is relatively fragile, and it may happen that:

  • Too much sugar regularly enters the bloodstream (you really like sweetened drinks, packed juices and other ultra-processed food).
  • The pancreas secretes more and more insulin so that the cells can absorb (and the liver can store) all that sugar from the blood.
  • Over time, the cells react to insulin less and less – more and more insulin is needed to absorb the same amount of sugar.
  • To help cells absorb sugar, the pancreas tries to produce more and more insulin.
  • Eventually, the pancreas is no longer able to produce the required amount of insulin, and blood sugar levels continue to rise.

A large amount of sugar in the blood is very harmful to the body, and therefore it must be moved to the cells as soon as possible or stored in the liver and muscles.

When all the “storages” are full, the liver sends the excess sugar to the fat cells, where it is stored as body fat.

This is how excess weight forms.

And what is even more serious – the prerequisites for the development of prediabetes and type 2 diabetes are being created.


What causes insulin resistance?

It is not clear what exactly causes insulin resistance and prediabetes, and although insulin resistance can also occur in people of normal weight, excess weight (especially around the waist) and lack of physical activity are currently considered to be the main risk factors.

Known causes of acquired insulin resistance:

  • Excess body fat. Obesity, especially visceral fat, is thought to be the main cause of insulin resistance. If your waist size is 40 inches (101.6 cm) or more for men and 35 inches (88.9 cm) or more for women, you are at increased risk of insulin resistance. This is because abdominal fat releases hormones and other substances that can promote chronic inflammation, which in turn can lead to insulin resistance.
  • Sedentary lifestyle. Physical activity makes your body more sensitive to insulin and builds muscle. The more muscles, the more sugar they consume and can absorb/store. Lack of physical activity has the opposite effect and can lead to insulin resistance. In addition, a sedentary lifestyle is usually associated with weight gain, which can also contribute to insulin resistance.
  • Ultra-processed foods high in carbohydrates and saturated fat have been directly linked to insulin resistance in many studies. These foods are quickly processed by the body – the carbohydrates in them cause a rapid increase in blood sugar. This puts extra strain on the pancreas and can lead to insulin resistance over time;
  • Some medications. For example – steroids, some blood pressure medications, certain HIV treatments, etc.

Other causes of insulin resistance:

  • Hormonal disorders. Our bodies produce hundreds of hormones that coordinate the various functions of our body. If their function is disrupted in any way, the system no longer works as intended, which in turn can affect how well our body uses insulin;
  • Some inherited genetic conditions can cause insulin resistance. For instance:
    • Type A Insulin Resistance Syndrome – a rare disease characterized by severe insulin resistance caused by defects in insulin receptor signalling.
    • Rabson-Mendenhall syndrome – a rare genetic disease characterized by growth retardation, lack of subcutaneous fat, and abnormal glucose homeostasis …
    • Donohue syndrome – is an extremely rare genetic disorder characterized by severe insulin resistance, prenatal growth restriction, postnatal growth failure and developmental delay …
  • Other hereditary conditions that can cause insulin resistance:
    • Myotonic dystrophy – a form of muscular dystrophy that affects the muscles, eyes and organs of the endocrine system, including the pancreas. Muscle sensitivity to insulin is reduced by about 70%.
    • Alström syndrome – a rare hereditary disease characterized by progressive vision and hearing loss, dilated cardiomyopathy, obesity, type 2 diabetes and short stature;
    • Werner syndrome – a rare progressive disease characterized by abnormally accelerated ageing (progeria);
    • Inherited Lipodystrophy – a condition where the body does not properly use and store fat.

What is the difference between insulin resistance and insulin sensitivity?

Insulin resistance and insulin sensitivity are closely related – if you have insulin resistance, you have low insulin sensitivity.

Conversely, if you are insulin sensitive, you have low insulin resistance.

Respectively – insulin resistance is harmful to your health, but increased sensitivity to insulin is beneficial.


What is the difference between insulin resistance and diabetes?

Short-term or chronic insulin resistance can develop in anyone.

If left untreated, chronic insulin resistance can eventually lead to prediabetes (blood glucose levels are higher than normal but not high enough to diagnose diabetes) and then to type 2 diabetes, the most common type of diabetes.


Type 2 diabetes occurs when the pancreas does not produce enough insulin or the sensitivity of your body’s cells to insulin decreases (insulin resistance), resulting in increased blood glucose levels.


Type 1 diabetes occurs when your body’s immune system attacks and destroys insulin-producing cells for an unknown reason. Type 1 diabetes is a chronic, autoimmune disease in which people must inject synthetic insulin to survive.

Type 1 diabetes is not caused by insulin resistance, but people with this disease can develop insulin resistance – when their body’s cells do not respond well to injected insulin.


Gestational diabetes is a temporary form of diabetes that can occur during pregnancy (insulin resistance is caused by hormones produced by the placenta). Gestational diabetes goes away after the baby is born. Gestational diabetes is diagnosed in approximately 3% to 8% of pregnant women.


Diabetes is usually diagnosed using a blood test that shows the average blood sugar level over the past three months (Hemoglobin A1C (HbA1c) Test):

  • An A1c level below 5.7% is considered normal;
  • An A1c level of 5.7% to 6.4% is considered prediabetes;
  • An A1c level of 6.5% or higher on two separate tests indicates type 2 diabetes.

What are the symptoms of insulin resistance?

If you have insulin resistance, but the pancreas can compensate by increasing insulin production, you will most likely not have any symptoms.

If your pancreas is unable to produce enough insulin, your blood sugar level rises (hyperglycemia), and the following symptoms may appear:

  • Increased thirst.
  • Frequent urination.
  • Increased hunger.
  • Blurred vision.
  • Headache.
  • Vaginal and skin infections.
  • Slow healing cuts and sores.

Many people have no symptoms of prediabetes for years before it develops into type 2 diabetes, but some may develop symptoms such as:


How to treat insulin resistance?

Factors contributing to insulin resistance, such as genetics and age, are not treatable.

Therefore, lifestyle and dietary changes are the main methods of treating insulin resistance, which include:

  • Healthy and balanced diet. Avoid excess carbohydrates (which stimulate excessive insulin production), eat less harmful fats and ultra-processed foods. Eat more vegetables, fruits, whole grains, fish and lean poultry.
  • Physical activity. Regular moderate-intensity physical activity helps increase glucose consumption and improve muscle sensitivity to insulin. A single moderate-intensity workout session can increase glucose uptake by at least 40%;
  • Excess weight reduction. This recommendation is more about preventing insulin resistance. For example, one study found that reducing excess weight by 7% can reduce the incidence of type 2 diabetes by 58%.

These dietary and lifestyle changes over time can:

  • Increase cell sensitivity to insulin.
  • Reduce blood glucose (sugar) levels.
  • Lower blood pressure.
  • Reduce triglycerides and LDL (“bad”) cholesterol.
  • Increase HDL (“good”) cholesterol levels.

Medicines to treat insulin resistance

Although there are currently no medications to treat insulin resistance directly, your doctor may prescribe medications to treat related conditions, such as:

  • Medicines for lowering blood pressure.
  • Metformin for diabetes.
  • Statins to lower LDL cholesterol.

Key takeaways

Insulin is essential for survival.

As long as your pancreas is able to produce enough insulin to compensate for the reduced response of cells to insulin, blood glucose levels will remain in a healthy range.

Insulin resistance is a complex condition that can affect your health in several ways. Because it has no symptoms until it turns into prediabetes or type 2 diabetes, the best thing you can do to prevent insulin resistance is to maintain a healthy weight by exercising regularly and eating a healthy, balanced diet.

Unfortunately, not all causes of insulin resistance can be prevented or treated. And while lifestyle and dietary changes can increase insulin sensitivity and reduce insulin resistance, not all causes of insulin resistance are reversible.

Insulin resistance can be one of the main causes of many chronic diseases, including type 2 diabetes, so preventing insulin resistance can be one of the most effective ways to live longer and healthier.


Be active, eat balanced and be healthy!


How does the pancreas work?

Hyperglycemia (High Blood Glucose)

Mechanisms of Insulin Action and Insulin Resistance

Recent Advances in Our Understanding of Insulin Action and Insulin Resistance

Insulin Resistance

The biology of human overfeeding

Metabolic Inflammation and Insulin Resistance in Obesity

The Association between Adult Weight Gain and Insulin Resistance at Middle Age: Mediation by Visceral Fat and Liver Fat

Visceral Fat: Culprit or Canary?

Insulin Resistance

Genetic Syndromes of Severe Insulin Resistance                                    

Insulin Resistance Syndrome

The Influence of Metabolic Syndrome in Predicting Mortality Risk Among US Adults: Importance of Metabolic Syndrome Even in Adults With Normal Weight

Effect of fructose consumption on insulin sensitivity in nondiabetic subjects

Fructose and hepatic insulin resistance

Update on the effects of physical activity on insulin sensitivity in humans

Insulin resistance is a cardiovascular risk factor in humans

Cardiovascular diseases

National Diabetes Statistics Report

American Diabetes Association Standards of Medical Care in Diabetes 2017

Long-term effects of lifestyle intervention or metformin on diabetes development and microvascular complications over 15-year follow-up: the Diabetes Prevention Program Outcomes Study

Acanthosis Nigricans

Metabolic Syndrome

Metabolic Syndrome. Also called: Insulin resistance syndrome, Metabolic syndrome X

High triglycerides to HDL-cholesterol ratio is associated with insulin resistance in normal-weight healthy adults

Blood Glucose and Insulin at Work

Diabetes Tests & Diagnosis

Understanding A1C

What is an insulin in blood test?

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