If you wanted to identify the single biological pattern most responsible for the diseases of modern Western adulthood, insulin resistance would be near the top of the list. It's the quiet engine behind pre-diabetes, type-2 diabetes, metabolic syndrome, fatty liver disease, much of cardiovascular disease, and a substantial fraction of age-related cognitive decline.

What insulin actually does

Insulin is the hormone that signals cells to take up glucose from the bloodstream. After a meal, blood glucose rises, the pancreas releases insulin, cells respond by absorbing glucose, blood sugar normalizes. This is the design.

Insulin also does many other things: it promotes fat storage, suppresses fat mobilization, signals the liver to stop producing glucose, and modulates dozens of other metabolic processes. It's a master regulator of energy storage and use.

What "resistance" means

Insulin resistance is the state where cells respond less efficiently to insulin's signal. The same amount of insulin produces less glucose uptake. To maintain blood sugar control, the pancreas compensates by producing more insulin.

For years, this compensation works. Blood sugar stays normal because there's enough extra insulin to brute-force the response. But the costs accumulate:

  • Chronically elevated insulin promotes fat storage, particularly visceral fat.
  • Elevated insulin makes fat mobilization harder — the "I can't lose weight no matter what I do" pattern.
  • Eventually, the pancreas can't keep up. Blood sugar starts rising. Pre-diabetes appears, then diabetes.
  • Insulin resistance also affects vascular function, brain function, and reproductive function — the cascading consequences extend well beyond glucose.

How to know if you have it

The fasting glucose test that most physicians order will look "normal" until insulin resistance is fairly advanced. The more sensitive markers are:

  • Fasting insulin — below 8 µIU/mL is healthy; above 10 suggests resistance.
  • HOMA-IR — calculated from fasting glucose × fasting insulin / 405. Above 2.5 indicates resistance.
  • Triglyceride-to-HDL ratio — above 2 in fasting state suggests resistance.
  • Waist circumference — above 102cm (men) / 88cm (women) correlates strongly.

Most physicians don't order fasting insulin routinely. Asking specifically is worthwhile.

What causes it

  • Excess visceral fat (the cause-and-consequence loop)
  • Sedentary lifestyle
  • Chronic over-consumption of refined carbohydrates
  • Sleep deprivation
  • Chronic stress
  • Some genetic predisposition
  • Aging itself (gradual decline starting around 30)

How to reverse it

The interventions that actually move insulin resistance:

  • Strength training (most leveraged)
  • Visceral fat reduction
  • Carbohydrate quality and timing
  • Walking after meals
  • Sleep optimisation
  • Reduced alcohol
  • Targeted supplementation (BalanceFlow's territory)

The honest summary

Insulin resistance is the upstream pattern behind most modern metabolic disease. It's mostly invisible until it's advanced. It's mostly reversible with the right interventions. The adults who address it in their forties live different metabolic lives in their sixties.