01 Insulin Resistance: What Your Blood Tests Reveal Early

Insulin resistance means your cells respond less strongly to the hormone insulin. Your body compensates for a long time by simply producing more insulin. That's why blood sugar often stays unremarkable for years, even though your metabolism is already shifting. The good news: few mechanisms in the body are as responsive to change as this one.

Many people only learn about their metabolism once "prediabetes" or "diabetes" appears on a lab report. Yet the story usually starts much earlier. A large British long-term study showed that insulin sensitivity and blood sugar change measurably years before a diagnosis ¹. Using those years well gives you the best possible head start.

What is insulin resistance?

Insulin resistance is a state in which the liver, muscles and fat tissue respond less sensitively to insulin. A simple picture helps: insulin is the key that unlocks your cells so they can take in sugar from the blood. After a meal, blood sugar rises, the pancreas releases insulin, and your cells absorb the sugar to use it for energy or store it.

With insulin resistance, the lock gets stiff. The key still fits, but it's harder to turn. To get enough sugar into the cells anyway, the pancreas produces more insulin. This works surprisingly well for a while. Blood sugar stays normal, and you don't notice a thing.

Your muscles play a special role here. They are the body's largest sugar store. A muscle cell that works regularly takes up sugar much more readily. That's one reason why endurance and strength training can influence insulin resistance so fundamentally ².

Why does insulin resistance go unnoticed for so long?

Because the body compensates for years, and standard blood sugar values only react late. The Whitehall II study, which followed thousands of British civil servants over many years, makes this timeline visible: in people who later developed type 2 diabetes, insulin sensitivity dropped markedly in the five years before diagnosis ¹. Fasting blood sugar rose only slowly at first and accelerated about three years before diagnosis ¹.

During this phase, the pancreas was still fighting back. Its insulin output briefly increased and only declined afterwards ¹. The researchers concluded that these metabolic changes begin three to six years before diagnosis, and that repeated measurements could help identify risk earlier ¹.

Which blood tests show insulin resistance?

No single routine blood test clearly shows insulin resistance. The most accurate method, the so-called clamp test, is complex and only used in research. In everyday practice, several blood markers are combined, each showing part of the picture.

Blood marker	What it shows	How to read it
Fasting blood sugar	How high your sugar is after a night without food	From 100 mg/dl, the Austrian guideline speaks of increased risk; from 126 mg/dl (on two days), of diabetes 2
HbA1c, the long-term blood sugar	Your average blood sugar over the past two to three months	Above 5.7% is considered prediabetes and should be followed up; from 6.5%, diabetes 2
Triglycerides and HDL cholesterol	How your body handles fats; high triglycerides and low HDL often occur together with insulin resistance	Not a diagnostic value on its own, but an important piece of the puzzle
TyG index	A formula combining triglycerides and fasting blood sugar to estimate insulin resistance	Promising, but without standard cut-offs yet 3
Fasting insulin and HOMA-IR	How much insulin your body needs to keep fasting blood sugar stable	Shows the pancreas's "overtime" directly

What matters is how these values interact. An HbA1c in the normal range is reassuring. But if your triglycerides are rising, your HDL is falling and your fasting blood sugar is slowly creeping up at the same time, a pattern emerges that deserves attention.

To be honest, research on some of these estimates isn't finished yet. A systematic review of the TyG index found good agreement with more complex methods, but rated the evidence as moderate and called for standard cut-offs before the index is widely used in clinics ³. That's exactly what researchers are working on. Until then, looking at several markers together and over time tells you more than relying on any single one.

What does belly fat have to do with insulin resistance?

A great deal. Fat stored deep in the abdomen around the organs, known as visceral fat, is considered an independent risk marker for type 2 diabetes and cardiovascular disease ⁴. It is more metabolically active than the fat directly under the skin and is closely linked to insulin resistance. Fat stored in the liver belongs in this picture too ⁴.

This has a practical consequence: body weight alone tells only part of the story. The Austrian diabetes guideline therefore recommends recording the ratio of waist circumference to height in addition to BMI ². A tape measure turns out to be a surprisingly useful tool.

Why is insulin resistance about more than sugar?

Because it is closely connected to other mechanisms. At speak23, insulin resistance belongs to the Metabolic health pillar, but it links directly to at least three other mechanisms:

• Liver function: Fatty liver and insulin resistance reinforce each other. Slightly raised liver values can therefore be part of the same pattern ⁴.
• Atherosclerosis risk: The typical blood lipid pattern in insulin resistance, high triglycerides and low HDL, affects blood vessels too ⁴.
• Silent inflammation: Visceral fat releases inflammatory messengers that can put additional strain on metabolism ⁴. That's exactly why looking at blood sugar alone isn't enough.

Can insulin resistance be reversed?

In many cases, yes, and that may be the most encouraging finding in preventive medicine. The Diabetes Prevention Program, a large randomised trial in the US, followed people with raised blood sugar for almost three years ⁵. Participants in the lifestyle programme had two goals: lose around 7% of their body weight and be active for at least 150 minutes a week. The result: their risk of developing type 2 diabetes fell by 58% compared with the placebo group ⁵. That was considerably more than the diabetes drug metformin achieved in the same study ⁵.

The Austrian guideline describes lifestyle change as the only sustainably effective prevention measure ². Among other things, it recommends [2]:

• at least 150 minutes of moderate endurance activity per week (or 75 minutes of vigorous activity),
• strength training on at least two days a week,
• no more than two days in a row without physical activity. The emphasis on strength training fits the picture above: more active muscle means more room for sugar. And getting there doesn't require a radical overhaul. Small changes, kept up consistently, can make the difference.

What can you do?

The first step is knowing your numbers. The decisive step is connecting them and sticking with it. Here's what that can look like with speak23:

1. See the whole mechanism. In the Core Health blood test, markers such as fasting blood sugar, HbA1c, triglycerides and HDL feed into the insulin resistance mechanism. You see not only individual values, but also how your metabolism connects with your liver, blood vessels and inflammation.
2. Spot early shifts. Because insulin resistance develops over years, the trend matters. With 2 or 4 tests a year, you can see whether your fasting blood sugar or blood lipids are slowly moving, long before a threshold is crossed.
3. Start with three recommendations, not twenty. You receive three evidence-based recommendations tailored to your blood results and your personal health history, such as your waist circumference, activity or sleep. They aim to move your values in the right direction.
4. See the effect. All results are recorded digitally and automatically. At your next test, the app shows how your changes are reflected in your results.
5. Have unusual results checked by a doctor. If your HbA1c is above 5.7% or your fasting blood sugar is 100 mg/dl or higher, the guideline recommends further testing ². You'll get specific questions to take to your doctor. speak23 doesn't replace a diagnosis. For more background, read our overview Understanding blood test results: why connections matter. How insulin resistance and blood lipids affect your blood vessels is the topic of the next part of this series on atherosclerosis risk.

Where is diabetes prevention heading?

Today's evidence is remarkably clear: metabolic changes begin years before a diagnosis ¹, and lifestyle changes can substantially lower diabetes risk in people with raised values ⁵. What remains open is how to reach the right people early enough, and how to help them keep changes going for years rather than weeks.

We believe this is where the future of prevention lies. Not in a single test that sounds the alarm once, but in ongoing support that makes shifts visible early and shows what your own choices achieve. Our approach at speak23 is to close that gap between a lab result and lasting change.

We are living longer than ever. Whether those extra years are healthy ones is decided to a large extent in our metabolism, long before we feel anything. That isn't a burden but an opportunity: few areas of health respond as clearly to what we do every day.

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