Insulin Resistance - what is it?

Insulin Resistance - what is it?

13 min read

Dr Suresh Khirwadkar

What is Insulin Resistance?

Often abbreviated to IR, Insulin Resistance is a state in the body where our insulin - a major hormone within the body - is not working as efficiently as it should do. This is bad for a number of reasons, which will be explained in this article.

Most of us know what insulin is and that it is important, but did you know you could be resistant to it? For years maybe without even knowing, as the symptoms are subtle and you may not even notice them.

Insulin resistance is important because it is a major cause of heart disease, high blood pressure, of course Type 2 Diabetes and weight gain and obesity, as well as a myriad of other symptoms that you may even be experiencing right now.

It can start from a very early age, in fact I regularly see it in children and teenagers in particular who see me with Acne. It is a major driver for obesity also and addressing it is usually the first step on a road to losing fat and treating obesity.

What are the symptoms of Insulin Resistance?

The symptoms depend entirely on the extent of the insulin resistance and how long you have had it for. You may have very little to no symptoms, or they could be very subtle, or you could have quite marked symptoms. If you have pre-diabetes (also known as borderline diabetes or impaired glucose tolerance) then you may have more symptoms.

If you have prediabetes it is very important that you work with your doctor to monitor and treat it, primarily through lifestyle measures.

Diabetes symptoms include:

  • Weight Gain
  • Frequent or increased urination
  • Feeling faint or dizzy or feeling 'the need for sugar'
  • Recurrent infections
  • More severe infections if you get once
  • Funny aches and pains
  • Changes in sensation in the hands or feet, such as tingling or numbness
  • Feeling hungry a lot of the time, even after eating
  • Poor skin and increased pigmentation around the neck, armpits and groins
  • Multiple skin tags around the neck and armpits

We know that some of these symptoms can also be present in people with prediabetes, usually just a lesser degree, but what about those with insulin resistance?

Well it's not particularly well understood or researched. It is still a relatively new area of medicine, as most of the focus has been on Type 2 Diabetes Mellitus (T2DM), and then pre-diabetes. Insulin Resistance is a relatively newcomer in to the world of medicine.

Because of this there is not an abundance of evidence as to what the symptoms of insulin resistance are, and there are relatively few case studies. However what I can tell you though is in my clinical practice I see many patients with Insulin Resistance (IR) and the symptoms they experience are varied, but mostly the above - just to a lesser degree. That is, except the weight gain.

Other symptoms of Insulin Resistance

Gaining Weight is not the only issue with Insulin resistance. IR can also cause lots of other symptoms and I certainly see this in my patients:

  • Fatigue, tiredness and lethargy
  • Aches and pains
  • Unexplained numbness or nerve pains
  • 'Need for sugar'
  • Dizzy spells
  • Chest pains
  • Muscle aches
  • Worsening arthritis or joint pains, even with no arthritis diagnosis
  • Poor concentration and memory

In fact almost all of those symptoms we put down to 'getting older' may be down to Insulin Resistance. After all, age is just a number right?

How do you test for Insulin Resistance?

Well the absolute gold standard test is the Euglycaemic Clamp Test but it is almost never done as it is totally impractical and really only done in a research setting.

There are other tests like:

  • HbA1c (diagnostic cut offs vary so check with your local doctor)
  • Oral Glucose Tolerance Test (OGTT)
  • OGTT with Insulins
  • Fasting glucose
  • Fasting glucose with fasting insulin (HOMA-IR)

I personally use the HOMA-IR a lot as it's incredibly practical, cheap and easily accessible. It is not 100% validated for every patient, but for those I mostly see, it is well validated. It gives a simple, easy to understand reading and for reference, although the link above suggests a score of 2.0 to be insulin resistance, other sites suggest a cut off of 1.6 may indicate IR, even lower such as 1.4

Let's talk about HbA1c (A1c)

The test is a very good, well standardised test across the world. It measures your glycosylated haemoglobin, that is to say, 'how sugary are your red blood cells?'. Given a Red Blood Cell survives for approximately 90 days - it is essentially a 3 monthly check of your blood sugars.

It is not perfect however. It has it's flaws.

The biggest is probably that whilst the test is incredibly well standardised, the diagnostic cut offs are not. Where I practice in Australia, the national guidelines suggest a cut off for pre-diabetes at 6.0%. It is the same in the UK where I trained, but in America for example they use a cut off of 5.7%.

In clinical practice I actually use a cut off of 5.5% as a 'pre pre diabetes' - AKA insulin resistance - because this is usually the point where when tracked, people's HbA1c starts to creep up - which is what we see with insulin resistance.

It is also a 3 monthly check, so there's no point repeating it too quickly to see changes (which can be disheartening for patients who want to see change), and in some places it's restricted (e.g. Medicare in Australia restrict it to once a year for non-diabetic patients).

HbA1c also is not diagnostic for insulin resistance. It can be affected in conditions such as Sickle Cell Anaemia (or other haemoglobinopathies) but it can also be elevated for reasons like chronic elevated cortisol - which isn't necessarily due to insulin resistance (although it will eventually cause it).

What about fasting glucose? My doctor said mine was fine?

Yes it might have been. But believe it or not, I've actually diagnosed patients with seemingly 'normal' fasting glucose levels who actually had T2DM - their glucose was fine, but their HbA1c told a more complete picture. I view fasting glucose a little like a broken clock - it's still correct twice a day.

In my humble opinion, a fasting glucose is useful for a super quick and easy screening test, but if you are doing a fasting glucose you should just do a fasting insulin and calculate a HOMA-IR as it's much more useful, then if the results are high do an HbA1c if you wouldn't have anyway.

Let's talk about weight

I will be writing a follow up piece on weight gain and insulin resistance, and how undoing it can be the biggest step to losing weight that you can take. It's a big topic, and one that needs its own article to do it justice.

For anyone interested I would recommend reading a book called The Obesity Code by Dr Jason Fung. It's a great read, and whilst I am not sure he's 100% there with his theories around IR and health, I think he is definitely on the right tracks.

In my practice almost all the patients I see for weight loss advice have very high levels of insulin resistance. It may be coincidence, but resolving the insulin resistance through proper diet and lifestyle measures like low-carb diets and intermittent fasting, the weight simply falls off them almost effortlessly.

In fact there is a ton of evidence that suggests patients who lose weight through intermittent fasting actually lose weight quicker, lose more fat (not just weight), and keep it off for a lot longer. This is compared to other patients on similar calorie deficits. We know that intermittent fasting (IF) is very good for IR (not confusing at all), so it stands to reason that reducing insulin resistance can lead to fat loss.

What causes Insulin Resistance?

The key to reversing it is to understand how it happened in the first place. I mentioned Dr Fung and his book - The Obesity Code - well in that he talks a lot about insulin resistance and how it develops. I think he does a good job explaining it.

There's 2 main reasons we become insulin resistant:

  1. Overconsumption of food and drink
  2. Lack of exercise

Let's break those down a little.


We are not talking calories here. Calories are important for weight gain/loss, but not really in the way you think. I will be doing a follow up post on this so monitor my blog for updates on that.

No in fact calories don't really come in to insulin much, if at all.

Too much high insulin foods

Insulin is released when we eat or drink something that is essentially not pure water. Almost everything will cause an insulin spike, though some foods much more than others. The amount that insulin rises with food and drink is called the Food Insulin Index (or Insulin Index for short) and whilst similar to the Glycaemic Index, it is different. There's a link on my files page where you can download a paper on it.

When we reach a certain level of insulin, our cells become 'resistant' to it. Insulin essentially 'forces' food into cells and at a certain point, they don't like that.

Think of insulin as someone trying to feed you. At the start it's fine, it's nice. But you get full, and after a while you don't want any more food. But they keep feeding you, in fact they start to force you. At some point you will start to resist that.

The higher insulin levels go, the higher resistance we gain.

Until levels start to fall, and then we lose resistance. The longer we go without insulin, the more resistance we lose.

Food isn't being shoved down your throat any more, so you don't need to resist the person as much.

This is what intermittent fasting is essentially doing - extending our time without insulin, thereby reducing insulin resistance even more

If however we eat foods that are too high in the insulin index (so called higher insulinogenic foods) then we will gain even more resistance. Think of those sugary snacks we all love - very high insulin activity. However it's not just sugar. We mentioned it's similar to the Glycaemic Index, but is't different. That's because it's not how much your sugars go up, but rather your insulin. For example, wholewheat bread is relatively low on the GI scale, but still quite high on the Food Insulin Index.

So we need to eat low insulin foods to maintain a low level of resistance.

Consuming too frequently

As we said above, this is what intermittent fasting is essentially undoing. The longer we go without consuming anything which raises our insulin levels, the more the insulin resistance will fall. If we consume too frequently, which we all do, then we will not allow the body to lower the resistance level enough, and we will start to climb.

There's debate on exactly how long it takes for insulin resistance to fall, but (spoiler) it's a long time. If it were, people wouldn't do longer intermittent fasting (e.g. 24 hours) or even prolonged fasts like 3-5-7 days as they wouldn't need to. There's a lot of evidence that insulin resistance falls to the lowest levels at around 72 hours of fasting - 3 days.

I'm not saying you must do a 3 day fast - you can - but please get medical advice first.

However it's generally accepted that we should not be consuming every 1-2 hours like we usually do. We should be allowing the body periods of rest from the insulin activity, and probably sticking more to the typical '3 square meals a day' paradigm. In fact probably 2 meals a day would be more beneficial for most people.


Exercise improves (reduces) insulin resistance, but not all exercise is created equal. There's a lot of evidence that resistance training in particular reduces insulin resistnace more than cardiovascular exercise. I saw this myself personally when I stopped lifting weights for a month because we were selling the house and had our gear in storage - my diet stayed the same, and even though I did cardio exercise, my HOMA-IR started creeping up, and fairly quickly.

Relaxation therapies such as Yoga and Pilates also lower insulin resistance. Quite exactly we aren't sure, but almost certainly as an interaction with another hormone - Cortisol.

Cardiovascular exercise also reduces insulin resistance, but not just any little exercise, you need to push it at least a little. Walking the dog is probably not going to be enough to keep it under control if your diet is not on point.

Resolving Insulin Resistance

I've personally seen most of the following when I resolved my insulin resistance (I had a Homa-IR score of around 2.8), and almost all of my patients who have resolved theirs also noted similar improvements:

  • Losing weight (fat) almost effortlessly
  • Less fatigue and tiredness
  • Less random aches and pains for no obvious reason
  • Wake up feeling refreshed
  • Better concentration and awareness
  • Memory improvements
  • Less hunger
  • Fewer cravings
  • Less pimples or Acne
  • Fewer funny rashes for no obvious reason
  • Much improved immune system

So how do we lower our insulin resistance?

Well it's undoing the above - reducing the overconsumption, reducing the insulin activity of our foods, and reducing the frequency of consumption of food and drinks to allow the body time to rest.

Intermittent fasting is a fantastic way to lower our insulin resistance levels (which is likely why it's so good for fat loss too) - although patients with medical conditions such as diabetes need to be careful about this - so please see your doctor first.

Metformin is a drug that can be useful to help lower insulin resistance also, and I do use it with some patients, though I prefer non-drug methods where possible.

I do help patients with this and am more than happy to consult with patients locally and across Australia (sorry I cannot consult outside of Australia) - click here for details

My personal and professional approach is the same.

I treat patients with insulin resistance the same as all my others - with care and attention, time and understanding. But the particular treatments - are those above.

Low(er) carb diets, Keto diets if wanted, intermittent fasting (not required but very beneficial), proper diet and nutrition advice, exercise advice including resistance training techniques (I usually recommend Starting Strength for beginners, and reducing the frequency of consumption.

I also recommend regular testing to help patients stay on track and see the difference they are making - usually using a HOMA-IR score - it will show changes very quickly, so particularly useful if people aren't 'seeing the benefits' - you can show them!

If you are interested in learning more about Insulin Reistance, PreDiabetes or Diabetes then consult with me or see your usual doctor for advice. You can also enrol on my 1-2 hour course on Insulin Resistance

Dr Suresh Khirwadkar is a Lifestyle GP specialising in all aspects of Primary Care, Skin Cancer, Psychology and Lifestyle Medicine. He did his undergraduate and post graduate training in the UK, currently practices in Australia and holds MBChB, BSc (HONS), MRCGP, FRACGP
Copyright 2022 Dr Suresh Khirwadkar
Disclaimer: Results are not guaranteed and can vary. Please speak to your Doctor about the most appropriate treatment for your medical conditions