There has long been an established link between insulin resistance and type 2 diabetes. Insulin resistance is the strongest predictor of the development of type 2 diabetes, and the consequences can be serious.
Estimates in the United States (US) of America suggest that it affects up to 24% of adults over 20 years old.
A 2015 Health Survey for England estimated that 10.7 percent of the English population (approximately 5 million people) are at increased risk of Type 2 diabetes, with an HbA1c between 42-46 mmol/mol.
Given that insulin resistance is a strong predictor of type 2 diabetes, and a raised HbA1c is diagnostic of diabetes, this is significant and demonstrates how common insulin resistance is.
In this article, we will explore what insulin resistance is, what the signs may be, the process of testing for insulin resistance, and finally will delve a little deeper into the big question that many people ask – can you reverse insulin resistance?
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What is insulin resistance?
To answer this question, we must first give an overview of what insulin is.
Insulin is a hormone produced in your pancreas, in the pancreatic beta-cells. The hormone insulin’s primary function is to assist the glucose in your bloodstream for energy by the cells in your liver, muscle, and adipose tissues. The glucose in your blood comes mainly from the food we eat (primarily carbohydrates). However, your liver can also make glucose in times of need, such as during fasting or starvation. Seeing a rise in your blood glucose levels (also called blood sugar levels) after eating is normal. When your pancreas is functioning well, your liver will release the right amount of insulin in response. This helps your blood sugar levels to remain in the normal range.
Insulin resistance can be described as critical cells in your liver tissue, adipose tissue (fat), and muscle tissue failing to respond well to insulin. When this happens, they cannot take up glucose from your blood. (This is a process that is needed so that glucose can be utilized for energy). Blood glucose levels can then build up, causing complications that can lead to certain signs and further health problems. These complications include but are not limited to type 2 diabetes.
We could ask what is happening when your body becomes insulin resistant? Simply put, your body is becoming resistant to the action of insulin. The glucose in your blood is then less able to get into the necessary body cells that are essential for energy production and regulation. Insulin resistance can further be explained as being:
A compromised biologic response to insulin stimulation of target tissues.
These target tissues are, as already mentioned, primarily the liver, muscle, and adipose tissues. When you are in a state of insulin resistance, the body is having difficulty clearing excess glucose in the body’s cells and tissues. As a result, there is a compensatory increase in insulin production from the pancreas, leading to hyperinsulinemia.
When your pancreas can repeatedly produce enough insulin, your blood glucose levels can remain in the healthy range. If measures are not taken to control your blood sugar levels and improve your insulin sensitivity, the pancreas becomes overworked. This is because it is attempting to combat consistently raised blood glucose levels. The pancreas attempts to do this by means of producing more insulin. Eventually, the pancreatic function becomes impaired. As a result, it stops producing enough insulin to control blood sugar levels, or the insulin it does produce is less effective. This leads to the development of prediabetes and then commonly, on to type 2 diabetes.
While there are differences between insulin resistance and type 2 diabetes, insulin resistance remains a key feature of this serious metabolic condition.
With early identification and management, insulin resistance and prediabetes can be better managed. There are also certain risk factors linked to insulin resistance that it is wise to be aware of to highlight any personal risk.
Signs of insulin resistance
Unfortunately, despite how common insulin resistance is, it is frequently present without displaying any signs and symptoms.
Acanthosis nigricans: One clinical sign that is linked to insulin resistance, however, is acanthuses nigricans. People who have prediabetes and insulin resistance may have the condition. Acanthosis nigricans is characterized by darkened skin in the armpit or on the back and sides of the neck. Some people also experience small skin growths called skin tags in these same areas. These dark, often velvety-looking patches of skin represent a manifestation of insulin resistance.
Retinopathy: A few research studies have shown the incidence of eye problems among this group of people. Usually attributed to those with diagnosed diabetes, damage to the vessels in the eyes can lead to something called retinopathy. Retinopathy is a serious complication. It occurs due to persistently high blood glucose levels. It is advised that if you notice any change to your vision, such as blurring, you seek professional medical help immediately. This is particularly pertinent if you also carry some of the risk factors for diabetes.
Metabolic syndrome: When there is a progression of insulin resistance, or insulin resistance remains untreated, this can lead to type 2 diabetes. Left untreated, insulin resistance can also lead to metabolic syndrome and non-alcoholic fatty liver disease.
Metabolic syndrome is a cluster of clinical diagnoses. These include high blood pressure, abnormal cholesterol levels, and large waist size. People who have metabolic syndrome are more likely to have prediabetes and thus go on to develop type 2 diabetes.
Symptoms of undiagnosed diabetes
While insulin resistance doesn’t usually cause signs and symptoms, undiagnosed type 2 diabetes commonly (although not always) does. Some of the common signs and symptoms of type 2 diabetes are:
- Needing to go to the toilet a lot
- Feeling very thirsty
- Fatigue or tiredness
- Tingling in your hands and/or feet
- Blurred vision
- Unexplained weight loss
- Prolonged healing of wounds
- Urine infections or genital itching/thrush
Risk factors for insulin resistance
Because insulin resistance frequently occurs in the absence of signs and symptoms, it is important that you know what the risk factors are. Much like for type 2 diabetes, there are risk factors associated with insulin resistance. These include
- Having metabolic syndrome
- Being overweight
- Or having a family history of the condition.
Insulin resistance can be more of a concern for people who have excess fat around their abdominal area. Crucially, it can also be a risk for people with established diabetes who inject insulin to manage their blood glucose levels. This can be people with either type 1 or type 2 diabetes.
It is commonly seen among teenagers with type 1 diabetes when their hormones are most unpredictable (8). It is also important to note that insulin resistance does not only occur in those who are overweight, and experiencing weight gain does not necessarily increase your risk. Other possible risk factors for the development of insulin resistance include:
- If you have heart disease
- Having polycystic ovary syndrome (also called PCOS – read more about PCOS symptoms here)
- Age (it is more common among people over 45 years old)
- Having gestational diabetes, or a history of gestational diabetes
- Being physically inactive
Unsurprisingly, insulin resistance is not without possible consequences and implications to your health. The main consequences of insulin resistance are:
- A high blood sugar level (also called hyperglycemia)
- Prediabetes and type 2 diabetes
- Raised blood pressure (hypertension)
- Dyslipidaemia (raised levels of fats in the blood
- An increased risk of inflammatory and prothrombotic states.
A prothrombotic state abnormality of blood coagulation increases the risk of thrombosis (blood clots in blood vessels). As already mentioned, hypertension and dyslipidemia are key features of metabolic syndrome. People with metabolic syndrome are also at an increased risk of cardiovascular disease. Suppose you have some or all of the features of metabolic syndrome, or you have a history of heart disease in your family. In that case, it is important that you seek professional medical advice to help assess your own risk and determine if further tests are needed.
Testing for insulin resistance
A blood test is essential to determine if someone has prediabetes. However, testing specifically for insulin resistance is less common and more complicated. A fasting plasma glucose test (FPG) is, however, frequently used to diagnose prediabetes.
Since 2011, the World Health Organisation (WHO) has declared that HbA1c can also be diagnostic of prediabetes and type 2 diabetes.
Less commonly, an oral glucose tolerance test (OGTT) will be carried out to diagnose prediabetes, although an OGTT is more commonly used to diagnose gestational diabetes.
It can be confusing to track all the different types of tests available for diagnosing prediabetes or diabetes. Your specialist healthcare team or your doctor will be able to advise you which test is most suitable for you.
A fasting plasma glucose (FPG) test is a simple blood test (taken from your arm) after several hours of fasting. Typically, an FPG test will be carried out in the morning, after fasting overnight while you sleep.
In the UK, the NHS advises people who are having a fasting glucose test not to eat or drink anything except water for 8 to 10 hours before their test time.
The WHO defines fasting plasma glucose test results to mean the following:
- Normal: Below 5.5 mmol/l (100 mg/dl)
- Impaired fasting glucose (IFG; a form of prediabetes): Between 5.5 and 6.9 mmol/l (between 100 mg/dl and 125 mg/dl)
- A diagnosis of diabetes: 7.0 mmol/l and above (126 mg/dl and above)
Always take advice from your doctor with regards to your personal test results.
Can insulin resistance be reduced or reversed?
Although there are some risk factors for developing insulin resistance that cannot be changed, such as age, ethnicity, and family history, there are some modifiable risks. Being more physically active, reducing your body weight (if necessary and safe to do so), and eating a healthier diet can all help to reduce your risk of developing insulin resistance and diabetes.
A core study called the Diabetes Prevention Programme saw older adults reduce their risk of developing diabetes by up to 70% in the US. This risk was reduced by interventions such as:
- Eating a healthier diet
- Losing 5-7% of body weight
- Taking medications such as metformin.
Whatever method you choose to improve your health and reduce the risk of insulin resistance, it is crucial to ensure you have support. A personalized approach is essential for achieving sustainable results. Having support from those close to you and professional, compassionate and safe guidance will make the journey easier. Diabetic patients and those at risk of the condition should attend regular medical appointments. They should also contact a healthcare professional if they are concerned about anything related to their health.
There are some clear links between the development of insulin resistance, prediabetes, and type 2 diabetes. Yet, there are also people with type 1 diabetes who experience insulin resistance, and it is linked to other factors other than bodyweight. It is a complex condition that is difficult to diagnose in isolation and can often go unnoticed. Lifestyle changes can help to reduce your risk of developing insulin resistance.