What Is Insulin Resistance

Overview

Insulin is a hormone the pancreas produces to regulate blood sugar levels in your body. Under normal conditions, it functions in the following manner:

• After a meal, your body breaks down food into glucose (your body’s primary energy source)
• Once glucose levels in the blood cross a threshold, the pancreas receives a signal to release insulin
• Insulin helps your muscles, fat, and liver cells absorb glucose for energy usage or storage
• Once blood glucose levels reduce, another signal is sent to the pancreas to halt insulin production¹

At times, various factors can interfere with the action of insulin on your body’s cells leading to a condition known as insulin resistance. 

Insulin resistance is the reduced responsiveness of your muscle, liver, and fat cells to normal insulin levels. It causes the pancreas to release more insulin to control rising blood glucose levels.^1,2

If your cells continue to become less sensitive to insulin, blood sugar levels will eventually rise, leading to prediabetes and Type 2 diabetes mellitus. Insulin resistance is also associated with other health conditions like:

• Cardiovascular disease
• Dyslipidaemia
• Hypercholesterolemia
• Hypertension (high blood pressure)
• Metabolic syndrome
• Non-alcoholic fatty liver disease (NAFLD)
• Obesity
• PCOS (Polycystic ovary syndrome)^1,2,3,4

Fortunately, insulin resistance can be treated and prevented. This article explains how, as well as every aspect of the disease.

Causes of insulin resistance

Researchers are still investigating how exactly insulin resistance develops. So far, they’ve discovered genetic mutations that interfere with insulin secretion and function.

Other factors believed to be significant contributors to insulin resistance include excess fat deposition (especially around the belly), lack of physical activity, and stress.^1,3

In general, the causes of insulin resistance are classified as:

• Acquired causes
  • Excess body fat: Studies have shown that excess fat around your belly and organs is the chief cause of insulin resistance. Fat deposition in your muscles and liver can lead to severe insulin resistance
  • The waistline measurements linked to insulin resistance are:
    • 40 inches or more for people assigned male at birth (AMAB)
    • 35 inches or more for people assigned female at birth (AFAB)
  • Body fat produces hormones and other substances that trigger inflammation which, in turn, contributes to insulin resistance
  • Physical activity: Exercise increases your body’s sensitivity to insulin. It also helps build more muscle to absorb more blood glucose. A lack of physical activity does the opposite and promotes weight gain, leading to insulin resistance
  • Diet: Eating highly processed, sugar-containing, high-carbohydrate and high-saturated fat food causes insulin resistance. These foods spike blood glucose levels when digested, putting the pancreas under stress to produce more insulin, leading to insulin resistance over time
  • Medications: Certain medicines can cause insulin resistance. They include steroids, some anti-hypertensives, certain HIV drugs, and some antipsychotics^1,2,4

• Hormonal causes, Certain hormonal disorders can interfere with insulin, causing insulin resistance. These include:
  • Acromegaly: It happens because of elevated levels of growth hormone. High levels of this hormone can cause an increase in glucose production, leading to insulin resistance
  • Hypothyroidism: It happens due to low levels of thyroid hormone. Since this hormone regulates your body’s metabolism (conversion of food into energy), fewer amounts of it cause a decrease in glucose metabolism, resulting in insulin resistance

• Genetic causes, Various inherited genetic conditions can cause insulin resistance. These include:
  • Type A insulin resistance syndrome (causes severe insulin resistance)
  • Type B insulin resistance syndrome  
  • Rabson-Mendenhall syndrome
  • Donohue syndrome
  • Myotonic dystrophy
  • Alström syndrome
  • Werner syndrome
  • Inherited lipodystrophy
  • Ataxia-telangiectasia²

Signs and symptoms of insulin resistance

There are no symptoms of insulin resistance so long as your pancreas can produce enough insulin to counter rising blood glucose levels. However, if your cells continue to be resistant, it could lead to hyperglycaemia (high blood sugar levels). 

Elevated blood sugar levels have noticeable symptoms that include:

• Frequent urination
• Excessive thirst
• High blood pressure
• Tingling in the hands and feet
• Fluctuations in body weight
• Blurry vision
• Fatigue
• Headaches
• Infections of the skin and vagina
• Wounds that heal slowly
• Cravings for sweet and salty foods
• Dark, dry skin on the groin, armpits, and back of the neck (Acanthosis nigricans)
• Skin tags 
• Abnormal eye changes that could result in diabetic retinopathy³

The last three symptoms are signs of prediabetes, a condition where blood sugar levels increase but not to the point of being diagnosed as diabetes. However, it could progress to type 2 diabetes over time.

Management and treatment for insulin resistance

The treatment options for insulin resistance include:

• Lifestyle modification, It is the primary treatment for insulin resistance since risk factors like age and genetics are not treatable. It involves:
  • Physical activity: Getting roughly 30 minutes of regular exercise five days a week improves your body’s insulin sensitivity and blood glucose usage. One session of moderate-intensity physical activity can boost your cells’ glucose uptake by at least 40%⁵
  • Healthy diet: The following eating habits promote insulin sensitivity
    • Eat low-glycemic index foods like vegetables, fruits, whole grains, nuts, fish, and lean meats. Studies confirm that DASH and Mediterranean diets help people with insulin resistance⁶
    • Avoid sugar, highly processed foods, red meat, carbohydrates, and saturated fats
    • Reduce calorie intake
    • Chew food slowly and stick to appropriate meal times and amounts
  • Weight loss: A study revealed that losing 5-7% of excess body weight boosts insulin sensitivity and delays the onset of diabetes by 60% in obese and overweight people.^2,3,4 

• Medications: At present, there are no medications to treat insulin resistance, however, healthcare providers may prescribe medicines to treat existing health conditions like diabetes, high blood pressure, and high low-density lipoprotein (LDL) cholesterol levels^1,2,3
• Weight loss surgery: Certain people with obesity can lose weight via surgical interventions like gastric sleeve, banding, and bypass to help ameliorate insulin sensitivity²

Diagnosis

Healthcare providers use several methods to diagnose insulin resistance. They use a combination of:

• A physical exam, assessment of symptoms, medical history, and family history
• Blood tests:
  • Glucose tolerance test (GTT): It determines if your body is properly using and storing glucose. It diagnoses Type 1 diabetes, Type 2 diabetes, and gestational diabetes
  • Glycated haemoglobin A1c test (HbA1C): It provides your average blood glucose levels over the past three months
  • Insulin tolerance test (ITT): It measures the sensitivity of your body’s insulin receptors to insulin by measuring blood glucose levels before and after insulin administration
  • Lipid panel: It consists of many tests that measure the levels of lipids like total cholesterol, high-density lipoprotein (HDL) cholesterol, LDL cholesterol, and triglycerides³

FAQs

How can I prevent insulin resistance

The ways you can prevent insulin resistance are:

• Staying at a healthy weight or losing weight by regularly exercising
• Eating a healthy diet and adhering to proper meal times
• Avoiding processed, sugary, high-carbohydrate, and high-saturated fat foods
• Avoiding alcohol and smoking
• Reducing stress and getting adequate sleep³

How common is insulin resistance

The best way to measure the prevalence of insulin resistance is through the number of metabolic syndrome cases since the two are closely linked.² According to the NHS, approximately 1 in 3 adults aged 50 and over suffer from metabolic syndrome in the UK.

Who is at risk of insulin resistance

The people at risk of developing insulin resistance:

• Are aged 45 or older
• Are obese or overweight (especially with excess belly fat)
• Have a family history of diabetes
• Have a medical history of gestational diabetes, heart disease, stroke, fatty liver disease, and sleep disorders
• Have high blood pressure and an abnormal lipid profile
• Have a sedentary lifestyle
• Are regular smokers 
• Have the following ethnicities:
  • Asian American
  • Black
  • Hispanic
  • Indigenous people from Alaska, the Pacific Islands, and the continental US

What can I expect if I have insulin resistance

Insulin resistance causes an increase in insulin levels (hyperinsulinemia) to maintain blood glucose levels within the normal range. Too much insulin can result in weight gain, which in turn, further worsens insulin resistance.

If left untreated, insulin resistance can progress to prediabetes and Type 2 diabetes. It is also a significant driving factor for obesity, high blood pressure, cardiovascular disease, and metabolic syndrome.^1,2,3,4

When should I see a doctor?

You should contact your doctor if you:

• Are experiencing symptoms of prediabetes or Type 2 diabetes
• Have medical condition/s associated with insulin resistance
• Have a family history of diabetes or medical condition/s related to insulin resistance

Summary

Insulin resistance is the inability of your muscles, liver, and fat cells to respond properly to insulin. Excess body fat and a lack of physical activity significantly contribute to insulin resistance. Over time, it can progress into prediabetes and Type 2 diabetes. It’s also a driving factor for several other diseases. The only way to treat and prevent insulin resistance is through lifestyle changes involving regular exercise, calorie restriction, weight loss, and a healthy diet. It’s best to contact your doctor to formulate a treatment plan if you are at risk of developing diabetes or have symptoms.