Insulin resistance is the process underneath most of what's on this site — type 2 diabetes, fatty liver, central weight gain and metabolic syndrome all trace back to it.
What it is
Insulin's main job is to move glucose from the blood into cells. Insulin resistance means cells respond less readily to that signal.
The body's response is to produce more insulin. For a time this works — glucose stays normal, and nothing appears on standard testing. This compensated stage can persist for years, which is why insulin resistance is usually well established before anything is detected.
Why it matters beyond glucose
Persistently high insulin has effects across the body:
It promotes fat storage, particularly visceral fat around the organs. Visceral fat is metabolically active, releasing inflammatory signals and fatty acids directly to the liver.
It drives liver fat. The liver stores excess energy as fat, and a fatty liver is itself less insulin-sensitive — a loop that reinforces itself.
It alters lipids — raising triglycerides, lowering HDL.
It contributes to raised blood pressure through several mechanisms.
That's four of the five metabolic syndrome criteria, from one process.
What causes it
Visceral fat — both a cause and a consequence. Physical inactivity — muscle is the largest site of glucose disposal, and inactive muscle takes up less. Genetics and ethnicity — significant, and not modifiable. Sleep — short or disrupted sleep, and untreated sleep apnoea, both worsen it. Some medications and conditions — including PCOS and certain hormonal disorders.
Can it be measured?
Not straightforwardly in routine practice. Direct measurement requires research-grade testing. Clinicians instead infer it from the pattern: waist circumference, triglycerides, HDL, blood pressure, glucose and HbA1c, and liver markers. Which is essentially what the metabolic syndrome criteria capture.
What improves it
Insulin sensitivity is genuinely responsive — and often improves faster than weight does.
Exercise has among the most direct effects, both aerobic and resistance training. Muscle contraction increases glucose uptake through pathways that don't require insulin at all, and the effect appears without weight change.
Losing visceral fat improves it substantially, and visceral fat is often lost preferentially early in weight loss.
Dietary pattern — reducing refined carbohydrate, added sugar and ultra-processed food.
Sleep — correcting short sleep and treating sleep apnoea.
Tools: Metabolic syndrome check · Type 2 diabetes risk check Related: Metabolic syndrome · Prediabetes · Liver health Next: Find a GP →
Educational information only. Not a substitute for medical advice — speak to a qualified health practitioner about your circumstances.