Insulin resistance: stop guessing, start testing
Insulin resistance has become the go-to explanation for almost every fat loss struggle. Can't drop weight? Must be insulin resistance. Cravings? Insulin resistance. Flat energy and poor carbohydrate tolerance? Same answer.
It is a real and important thing. It is also, very often, blamed without anyone ever measuring it.
That is the problem. Not that insulin resistance is irrelevant, because it matters a great deal. The problem is treating it as the default reason the scale will not move, with no objective evidence behind the assumption. Here is how to think about it properly, and how one simple blood marker can either confirm it or rule it out.
What insulin resistance actually is
Insulin resistance describes a state where your cells respond less effectively to insulin. To keep blood glucose in range, the pancreas compensates by producing more insulin. Over time, that pattern is linked to higher metabolic risk, including type 2 diabetes and cardiovascular disease, particularly alongside excess body fat, inflammation, poor diet quality and low physical activity (Gayoso-Diz et al., 2013).
So it is worth taking seriously. But taking it seriously is not the same as it being the reason you specifically are not losing fat. Those are two different claims, and only one of them can be tested.
HOMA-IR: putting a number on it
This is where HOMA-IR earns its place. HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It is a calculation built from two fasting blood markers, glucose and insulin, and it gives a practical estimate of how insulin resistant or insulin sensitive someone is (Matthews et al., 1985).
It is not the gold standard. That title belongs to a clamp study run in a research lab. But HOMA-IR was validated against those clamp measurements and tracks them closely, which is why it is used so widely in clinics and research from a single fasting blood test (Matthews et al., 1985).
The test is straightforward. After an overnight fast, glucose and insulin are measured. Glucose tells you how much sugar is in the blood at that moment. Insulin tells you how hard the body is working to keep it there. Read together, they say far more than glucose alone.
That last point is the one most people miss. Fasting glucose can look completely normal while fasting insulin is quietly elevated. The body is holding the line on glucose, but only by pumping out more insulin to do it. Glucose on its own misses that. HOMA-IR catches it.
Why one number still needs context
Higher HOMA-IR generally means more insulin resistance. But there is no single universal cut-off that works for everyone. The threshold shifts with age, sex, body weight, ethnicity and clinical context, and the studies that have tried to pin down the number land in different places depending on the population (Gayoso-Diz et al., 2013). So the score is one input into a bigger picture, not a verdict on its own. Interpreting it properly is a job for a qualified professional, not a calculator, and diagnosis and any medical management sit with your doctor.
Test, do not assume
Here is the practical shift. If you are struggling to lose fat, insulin resistance could be part of the story. It is not automatically the story.
Fat loss stalls for far more ordinary reasons. Inconsistent intake. Inaccurate tracking. Big weekends quietly undoing the week. Low daily movement. Poor sleep. High stress. Alcohol. Training output dropping without you noticing. Low fibre. And plain water fluctuations being misread as fat gain.
This is why testing beats guessing. If HOMA-IR comes back elevated, the plan can prioritise the levers that genuinely support insulin sensitivity: improving body composition, more physical activity, more fibre, better carbohydrate quality, less alcohol, better sleep and a more consistent training structure. The evidence for that direction is strong. In a landmark trial, an intensive lifestyle program built on modest weight loss and regular activity cut progression to type 2 diabetes by 58 percent, outperforming medication (Knowler et al., 2002).
If HOMA-IR comes back normal, that is just as useful. It tells you insulin resistance is probably not the thing holding you back, so you stop chasing it and look at the real limiter instead: total energy intake, weekly adherence, training load, recovery, or one of the ordinary factors above.
Testing does not only find problems. It rules out the wrong explanation, which is often the more valuable result.
The same logic runs through your bloodwork
Insulin resistance is simply the clearest example of a broader principle. Low iron is not fixed by randomly taking iron. Poor lipid markers are not fixed by vaguely eating clean. Raised inflammatory markers do not automatically call for an anti-inflammatory supplement. Every one of these needs the same approach. Assess first, interpret in context, then act.
Bloodwork does not replace the basics. Energy balance, protein, fibre, food quality, training, sleep and consistency still do the heavy lifting. But it can tell you whether your internal environment supports your goal, whether a hidden constraint is in play, or whether a popular explanation is unlikely to be the real one.
Better data leads to better decisions.
The bottom line
Insulin resistance is a genuine metabolic concern, not a catch-all excuse for every hard fat loss phase. If you suspect it, measure it. If the data backs it, build the plan around it. If it does not, move on and find the actual limiting factor.
If your body is not responding the way you think it should, and you want to understand what your bloodwork, body composition and nutrition are actually telling you, book a discovery call. We will map out what needs assessing, what might be limiting your progress, and what the next step looks like.
References
Gayoso-Diz, P., Otero-González, A., Rodriguez-Alvarez, M.X., Gude, F., García, F., De Francisco, A. and González Quintela, A. (2013) 'Insulin resistance (HOMA-IR) cut-off values and the metabolic syndrome in a general adult population: effect of gender and age: EPIRCE cross-sectional study', BMC Endocrine Disorders, 13, p. 47. Available at: https://doi.org/10.1186/1472-6823-13-47.
Knowler, W.C., Barrett-Connor, E., Fowler, S.E., Hamman, R.F., Lachin, J.M., Walker, E.A. and Nathan, D.M. (2002) 'Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin', New England Journal of Medicine, 346(6), pp. 393 to 403. Available at: https://doi.org/10.1056/NEJMoa012512.
Matthews, D.R., Hosker, J.P., Rudenski, A.S., Naylor, B.A., Treacher, D.F. and Turner, R.C. (1985) 'Homeostasis model assessment: insulin resistance and beta-cell function from fasting plasma glucose and insulin concentrations in man', Diabetologia, 28(7), pp. 412 to 419. Available at: https://doi.org/10.1007/BF00280883.