Insulin Resistance: What It Is, and Why It Isn’t Your Fault

If you’ve been feeling tired, foggy, or stuck at a weight that won’t budge no matter how virtuous your salads have been, insulin resistance might be part of the picture. It’s common, it’s manageable, and understanding it is the first step to doing something about it, rather than just glaring at the bathroom scale like it owes you money.

So, What Actually Is Insulin Resistance?

Your body is incredibly clever. Like, genuinely impressive - it’s running thousands of processes right now without you lifting a finger. One of its most important jobs happens every time you eat.

When you eat, your blood sugar rises and your pancreas releases insulin, a hormone whose entire career is dedicated to ushering glucose out of your bloodstream and into your cells, where it can actually be put to work. ^[1] Picture insulin as a key, and your cells as doors with very particular locks. Under normal conditions, the key slides in, the door swings open, sugar wanders in like it owns the place, and everyone gets on with their day. It’s a tidy little system, and most of the time you don’t even notice it’s running.

Insulin resistance is what happens when those locks start to stick. The cells stop answering the door properly, so sugar hangs around in the blood instead of being let in. The pancreas, ever the overachiever, notices and responds the way overachievers do: by trying harder. It pumps out more insulin, and for a while this brute-force approach works well enough that blood sugar looks perfectly normal on paper, even though something underneath is clearly puffing to keep up. ^[2] Eventually the pancreas can’t keep shouting louder to be heard, and blood sugar starts creeping upward.

None of this is a character flaw or a failure of willpower. Your cells are being difficult. You, personally, are not the problem here.

How Insulin Resistance Affects the Body

Insulin doesn’t stick to one job description, so when it stops working properly, the fallout tends to spread. Think of it like one domino tipping others over, except less fun to watch. Here’s where the pieces tend to land.

Muscles

Skeletal muscle is normally the biggest consumer of glucose in the body, basically the family member who eats the most out of the fridge without ever being asked. When muscle cells turn a cold shoulder to insulin, they take up less sugar for fuel, which is part of why persistent fatigue is such a common complaint, even in people who technically slept fine and have no obvious reason to feel like they’ve been hit by a bus.

Liver

Unable to shuttle sugar into muscle as efficiently, the body improvises and converts the surplus into fat, some of which gets stashed away in the liver itself. Over time this can contribute to fatty liver disease, a name so mild-mannered it almost sounds like something you’d order at a deli, when in fact it is actually quite serious.

Belly Fat

Fat carried around the abdomen isn’t just sitting there quietly minding its own business. Visceral fat is metabolically active tissue that pumps out inflammatory chemicals, and that inflammation goes on to make insulin resistance worse, which then encourages more of this kind of fat to stick around. Yes, belly fat is actively working against you.

Rude.

Heart and Blood Vessels

Insulin resistance tends to raise triglycerides, lower HDL (the “good”) cholesterol, and push blood pressure up, a combination that raises long-term cardiovascular risk. Your heart is far too polite to complain out loud, but it is absolutely taking notes.

Hormones

In women, insulin resistance is closely tied to polycystic ovary syndrome. Elevated insulin can prompt the ovaries to produce more androgens, contributing to irregular cycles, acne, and unwanted hair growth, and the relationship runs both ways, with the hormonal shifts of PCOS also feeding back into insulin resistance. As if hormones weren’t already complicated enough.

Brain

Insulin receptors exist throughout the brain, and there’s growing evidence that insulin resistance affects memory and cognitive function, with some research pointing to a link with Alzheimer’s disease risk. ^[3] So if you’ve been walking into rooms lately and immediately forgetting why, it might not just be that you’re busy. Your blood sugar could genuinely be part of the plot.

What Are the Symptoms?

One of the trickiest things about insulin resistance is that it’s often silent in the early stages. ^[1] It doesn’t announce itself with a dramatic entrance - it quietly sets up camp while you go about your life.

As it progresses, you might notice some of these signs:

• Feeling persistently tired or flat, even after a full night’s sleep (the kind of tired that coffee is no longer fixing)
• Strong cravings for sugar or refined carbohydrates, as though your body is staging a small protest
• Weight gain concentrated around the abdomen that shrugs off effort
• Brain fog - difficulty concentrating, feeling mentally slow, losing your train of thought mid-senten….
• Mood swings or irritability (your loved ones may have noticed this one before you did)
• Increased thirst and more frequent trips to the bathroom
• Dark, velvety patches of skin at the neck, armpits, or skin folds, known as acanthosis nigricans ^[4]
• Skin tags, uninvited but generally harmless

None of these symptoms belong exclusively to insulin resistance, which is exactly why testing beats guesswork.

What Causes It?

There’s rarely one single villain in this story. It tends to build slowly, through a combination of daily habits, health history, and a few things you simply arrived with (thanks, genetics).

Lifestyle Factors

• A diet heavy on processed foods, refined carbohydrates, and sugary drinks
• Not enough movement or physical activity
• Carrying excess weight, particularly around the abdomen
• Poor or insufficient sleep, which your body takes far more personally than you’d expect
• Chronic stress, which raises cortisol and, in turn, blood sugar - stress really is the gift that keeps on giving, isn’t it?

Health-Related Factors

• Polycystic ovary syndrome ^[9]
• Chronic inflammation or autoimmune conditions
• A history of gestational diabetes

Factors Outside Your Control (so no blame here)

• A family history of type 2 diabetes
• Getting older - risk naturally increases with age, because apparently ageing wasn’t already bringing enough to the party
• Ethnicity - in New Zealand, type 2 diabetes is more common among Māori, Pacific, and South Asian peoples ^[5]

How Is Insulin Resistance Tested?

Here’s a fun fact: insulin resistance doesn’t come with a flashing warning light. There’s no single test that simply says “yep, that’s it.” ^[6] Instead, your practitioner will look at a combination of clues - a bit like being a health detective, but with less trench coat and more blood tests.

Clinical Assessment

This usually starts with a conversation about your symptoms, a waist measurement, a blood pressure check, and a look for physical signs such as darkened skin patches. Unglamorous, but genuinely useful.

Fasting Blood Tests

Most of the useful information comes from a fasting blood sample - meaning you’ve had nothing to eat for around 8-10 hours beforehand (water is fine, and yes, black coffee is a whole separate philosophical debate). Your practitioner may check:

• Fasting blood glucose - can look perfectly innocent in the early stages, since the pancreas is often still compensating behind the scenes
• Fasting insulin - elevated levels, even with normal glucose, can be an earlier tell than glucose itself
• HOMA-IR - a calculation combining fasting insulin and fasting glucose to estimate how well insulin is actually doing its job ^[7]
• HbA1c - reflects average blood sugar over roughly three months, useful for spotting prediabetes, though it can miss earlier insulin resistance while glucose is still being propped up within a normal range ^[8]
• Lipid panel - insulin resistance tends to produce a recognisable pattern: higher triglycerides (blood fats) and lower “good” HDL cholesterol. Your lipid results can quietly tell a story your glucose levels haven’t started telling yet.

The Key Takeaway on Testing

Because standard glucose and HbA1c results can look reassuringly normal well into the process, it’s worth asking specifically about a fasting insulin test if you have symptoms or risk factors, rather than leaning on glucose alone. The earlier insulin resistance is caught, the more room there is to turn it around.

The Good News

Insulin resistance responds well to lifestyle changes, often significantly and sometimes fully. Regular movement, whole-food eating patterns, better sleep, and stress management have all been shown to improve insulin sensitivity, and in many cases the condition can be substantially reversed rather than simply managed. ^[1] Your cells, it turns out, are willing to make up.

You don’t need to overhaul everything overnight, and you definitely don’t need to figure it out alone with nothing but a search engine and a growing sense of dread. If any of this sounds familiar, or you’d simply like a second opinion on your own blood work, book a time to come in for a chat. Small, well-targeted changes tend to make a bigger difference than people expect, and your pancreas has already been working hard enough without an audience.

References

1. Centers for Disease Control and Prevention (CDC). About Insulin Resistance and Type 2 Diabetes. https://www.cdc.gov/diabetes/about/insulin-resistance-type-2-diabetes.html
2. Insulin Resistance. StatPearls. National Center for Biotechnology Information (NCBI). https://www.ncbi.nlm.nih.gov/books/NBK507839
3. Brain insulin resistance and cognitive function: influence of exercise. PubMed Central. https://pmc.ncbi.nlm.nih.gov/articles/PMC9744647
4. Obesity and Insulin Resistance: Symptoms, Diagnosis, and Treatment. Obesity Medicine Association. https://obesitymedicine.org/blog/obesity-and-insulin-resistance
5. Health New Zealand | Te Whatu Ora. Diabetes in Aotearoa New Zealand. https://www.healthnz.govt.nz/health-professionals/guidance- standards/topic/conditions/diabetes
6. Insulin Resistance - Workup and Diagnosis. Medscape Reference. https://emedicine.medscape.com/article/122501-overview
7. HOMA-IR (Homeostatic Model Assessment for Insulin Resistance). MDCalc. https://www.mdcalc.com/calc/3120/homa-ir-homeostatic-model-assessment-insulin- resistance
8. Pitfalls of HbA1c in the Diagnosis of Diabetes. The Journal of Clinical Endocrinology & Metabolism, 2020. https://pmc.ncbi.nlm.nih.gov/articles/PMC7335015
9. Insulin resistance in polycystic ovary syndrome across various tissues: an updated review of pathogenesis, evaluation, and treatment. Journal of Ovarian Research, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC9832677
10. Visceral fat and insulin resistance - what we know? PubMed. https://pubmed.ncbi.nlm.nih.gov/30398218