Insulin Resistance: Symptoms, Causes, Testing and How To Reduce It

We see many patients in clinic with symptoms of low insulin sensitivity so we thought it would be timely to take a look at Insulin and more specifically, insulin resistance. Many people have heard the term but are not always clear on what it actually means, how it affects the body or why it can increase the risk of serious long-term health problems.

Insulin resistance is increasingly common and can develop gradually over time. It may contribute to fatigue, cravings, weight gain, difficulty losing weight and unstable energy levels long before a person is diagnosed with prediabetes or type 2 diabetes. The good news is that with the right support, testing and lifestyle changes, insulin resistance can often be improved significantly.

In this blog, we explain what insulin is, how insulin is used in the body, what insulin resistance is, what causes it, the symptoms to watch for, how it is linked to diabetes, whether it can cause weight gain and how to test for and reduce insulin resistance.

By Nyanda Dennison, Clinical Nutritionist and Nutrition Coach

What Is Insulin?

Insulin is a hormone made by the pancreas. Its main role is to help regulate the amount of glucose in the bloodstream.

When we eat carbohydrates, our body breaks them down into glucose (sugar), the glucose enters our bloodstream and causes our blood glucose levels to rise. In response, the pancreas releases insulin to help move that glucose from the blood into the body’s cells, where it can be used for energy or stored for later use.

Without insulin, glucose remains in the bloodstream instead of reaching the cells that need it. This is why insulin is so important for maintaining healthy blood sugar levels and supporting normal energy production.

How Is Insulin Used In The Body?

Insulin acts a bit like a key. It helps unlock the cells so glucose can move from the bloodstream into muscle, liver and fat cells.

Once inside the cells, glucose can be:

• used immediately for energy
• stored in the liver and muscles as glycogen
• converted into fat for longer-term energy storage if there is an excess

When you haven’t eaten for a few hours blood glucose levels drop below normal and the pancreas releases a second hormone, called glucagon, which has the opposite effect of insulin. Glucagon converts the glycogen (out of the liver and muscle cells) back to glucose to use for energy and encourages fat burning.

In a healthy system, insulin and glucagon work together to keep blood sugar within a balanced range. Unfortunately for many people this process is disrupted by a condition called insulin resistance.

What Is Insulin Resistance?

Insulin resistance happens when the body’s cells stop responding to insulin. The pancreas may still produce insulin, sometimes in high amounts, but the cells do not respond as effectively as they should.

As a result, glucose is not moved out of the bloodstream efficiently. To compensate, the pancreas releases more insulin in an attempt to keep blood sugar under control, which results in high glucose AND high insulin in the bloodstream.

This is important because insulin resistance can exist for years before blood sugar becomes obviously abnormal on routine testing. Not only does high blood glucose make you feel awful… but it is also dangerous and can cause:

• Weight gain
• Cravings
• Irritability & depression
• Fatigue
• Poor concentration & memory
• and if not addressed, Type 2 diabetes and / or heart disease

What Is The Link Between Insulin Resistance And Diabetes?

Insulin resistance is one of the key drivers of type 2 diabetes.

In the earlier stages, the pancreas can often keep up by producing more insulin. This may keep blood glucose levels within a near-normal range for a period of time. However, if insulin resistance continues and the pancreas can no longer meet the increased demand, blood glucose begins to rise more consistently.

This progression often looks like this:

1. Insulin resistance develops
2. Insulin levels rise to compensate
3. Blood glucose starts to creep up
4. Prediabetes may develop
5. Type 2 diabetes may follow if it is not addressed

Not everyone with insulin resistance will go on to develop type 2 diabetes. However, it does increase the risk, especially when combined with other factors such as excess body fat, poor diet, chronic stress, low physical activity, sleep disruption or a family history of diabetes.

What Causes Insulin Resistance?

But what causes this condition, and what are the symptoms to watch out for?

The exact causes of insulin resistance are not fully understood. It is usually influenced by a combination of factors rather than one single cause. Some of the most common contributors include:

Excess body fat

Carrying excess weight, particularly around the abdomen, is strongly associated with insulin resistance. Visceral fat around the organs is especially linked to poorer insulin sensitivity.

Sedentary lifestyle

Physical inactivity reduces the body’s ability to use glucose effectively. Regular movement helps muscles become more responsive to insulin.

Diet high in refined carbohydrates and added sugars

A dietary pattern high in processed foods, sugary snacks, soft drinks and refined carbohydrates may contribute to blood sugar spikes and increased insulin demand.

Chronic stress

Long-term stress can increase cortisol and other stress hormones, which may affect blood sugar regulation and worsen insulin resistance over time.

Poor sleep

Inadequate or poor-quality sleep can disrupt hormones involved in appetite, metabolism and insulin sensitivity.

Genetics and family history

Some people may be more genetically predisposed to insulin resistance and type 2 diabetes.

Hormonal and medical conditions

Conditions such as polycystic ovary syndrome (PCOS), metabolic syndrome and non-alcoholic fatty liver disease are often linked with insulin resistance.

Inflammation

Low-grade chronic inflammation may also play a role in disrupting normal insulin signalling.

Understanding the causes and symptoms of insulin resistance is the first step towards managing and treating this condition.

Can Insulin Resistance Cause Weight Gain?

Insulin resistance can make weight gain more likely and can also make weight loss feel more difficult.

This is partly because insulin is a storage hormone. When insulin levels remain elevated, the body is more likely to store energy rather than burn it. High insulin levels may also increase hunger, cravings and energy dips, which can make it harder to maintain balanced eating habits.

People with insulin resistance often describe:

• strong cravings for sugar or refined carbohydrates
• feeling hungry again soon after eating
• afternoon energy crashes
• difficulty losing weight despite trying to eat well
• a tendency to gain weight around the middle

Weight gain can worsen insulin resistance, which can create a frustrating cycle. This is one reason why early intervention is so important.

What Are The Symptoms Of Insulin Resistance?

Insulin resistance does not always cause obvious symptoms in the early stages. However, there are several signs that may suggest blood sugar regulation is not working as well as it should.

Common insulin resistance symptoms may include:

• fatigue or low energy
• sugar cravings
• increased appetite
• difficulty losing weight
• weight gain, especially around the abdomen
• brain fog or poor concentration
• irritability or mood swings
• feeling shaky, light-headed or hungry between meals
• afternoon slumps
• disrupted energy after eating
• skin changes such as skin tags or darker patches of skin, particularly around the neck or underarms
• irregular periods or fertility issues in some women, especially with PCOS

These symptoms can overlap with other health issues, which is why proper assessment is important.

How To Test For Insulin Resistance

If insulin resistance is suspected, testing can help build a clearer picture. There is no single perfect test for everyone, and the most suitable option will depend on the person’s symptoms, health history and clinical presentation.

Insulin resistance tests that may be used include:

Fasting blood glucose

This measures blood sugar after an overnight fast. It can identify elevated blood glucose but may not detect earlier insulin resistance on its own.

HbA1c

A HbA1c test shows average blood glucose levels over the previous two to three months and can help identify prediabetes or diabetes.

Fasting insulin

This can provide insight into how much insulin the body is producing to maintain blood sugar control. In some cases, insulin may be elevated before glucose levels become abnormal.

HOMA-IR

This is a calculation that uses fasting glucose and fasting insulin to estimate insulin resistance.

Oral glucose tolerance test

This measures how the body handles glucose over time after drinking a glucose solution. It can be useful in some cases where blood sugar dysregulation is suspected.

Additional metabolic markers

A practitioner may also consider cholesterol, triglycerides, liver markers, waist circumference, blood pressure and other signs of metabolic dysfunction.

Testing should always be interpreted in context. A normal result on one marker does not always rule out early problems with insulin sensitivity.

How To Reduce Insulin Resistance

The good news is that insulin resistance can often be managed and even reversed with the right treatments and lifestyle changes. In many cases, these changes can have a significant impact on blood sugar control, energy and long-term health risk.

Focus on balanced meals

Meals that include protein, healthy fats and fibre can help slow the release of glucose into the bloodstream and improve satiety.

Choose better-quality carbohydrates

Carbohydrates are not the enemy. However, the type and quantity matter. Choosing less processed carbohydrates and paying attention to portion balance can support more stable blood sugar levels.

Examples include:

• oats
• legumes
• quinoa
• sweet potato
• brown rice
• fruit in sensible portions
• non-starchy vegetables

Reduce highly processed foods

Frequent intake of sugary drinks, sweets, pastries, white bread and ultra-processed snacks may worsen blood sugar instability and increase insulin demand.

Exercise regularly

Both aerobic exercise and resistance training can improve insulin sensitivity. Even walking after meals can be helpful.

Support healthy body composition

Losing even a modest amount of excess weight can improve insulin sensitivity in many people.

Prioritise sleep

Aim for consistent, restorative sleep where possible. Sleep plays a major role in appetite regulation, glucose control and metabolic health.

Manage stress

Chronic stress can worsen blood sugar regulation. Strategies such as mindfulness, breathing exercises, gentle movement and time outdoors may help.

Is Insulin Resistance Reversible?

In many cases, insulin resistance can be improved and sometimes significantly reversed, especially when it is identified early. That said, this depends on the underlying causes, how long it has been present and how consistently treatment strategies are applied.

The goal is not simply to lower blood sugar in the short term. It is to improve how the body responds to insulin and address the broader metabolic patterns contributing to the problem.

FAQs About Insulin Resistance

When To Seek Support

Insulin resistance can have many drivers, so a personalised plan is often more effective than a one-size-fits-all approach. If you are dealing with fatigue, cravings, brain fog, weight gain, unstable energy or concerns about blood sugar regulation, it may be worth exploring whether insulin resistance is playing a role.

If you believe you are struggling with blood glucose regulation or suspect you may have insulin resistance, book in with Nyanda, one of our Clinical Nutritionists, who will review your current symptoms, identify if an insulin resistance test is required and support you to get your health back on track and avoid any potential further complications.