What it means
Insulin is the hormone that tells muscle and fat to take up glucose and tells the liver to stop making it. Insulin resistance is when those tissues respond less, so the pancreas secretes more insulin to get the same effect. Blood glucose stays normal for years at the cost of high insulin; eventually the pancreas cannot keep up, glucose rises and the diagnosis is prediabetes or type 2 diabetes.
The main causes are excess visceral fat and liver fat, inactivity (muscle is the largest glucose sink), sleep loss and chronic inflammation. Genetics set the threshold; behaviour decides whether you reach it.
Why it matters for longevity
High insulin itself drives harm before glucose moves: it raises ApoB particle count and triglycerides, raises blood pressure, promotes fat storage, keeps mTOR switched on and is linked to several cancers and to cognitive decline. Reversing insulin resistance is probably the single highest-yield metabolic intervention available to most adults.
What the evidence says
The Diabetes Prevention Program (2002, 3,200 people with prediabetes) showed that lifestyle change — 7% weight loss and 150 minutes of weekly activity — cut progression to diabetes by 58% over three years, beating metformin (31%). The DiRECT trial (2018) put type 2 diabetes into remission in 46% of participants through weight loss alone, rising to 86% among those who lost 15 kg.
Muscle is central: a single session of resistance or endurance exercise improves insulin sensitivity for 24–48 hours, and training builds the capacity. Sleep restriction to four hours for a week reduced insulin sensitivity by about 20% in healthy young men (Spiegel 1999) — reversibly.
How to measure or use it
- Fasting insulin (target under 6 µIU/mL) and HOMA-IR (under 1.5) catch it early; HbA1c and fasting glucose catch it late. Triglyceride-to-HDL ratio above 2 (mg/dL) is a useful hint.
- Waist circumference and a DEXA visceral-fat estimate track the main cause.
- Reversal in rough size: fat loss of 5–15% of body weight, then resistance plus endurance training, then sleep, then diet composition. Most people see HOMA-IR fall within 8–12 weeks.
Related
- Metabolic health — the full article
- The fat-loss protocol — where it is the main lever
- GLP-1 transition guide — if a GLP-1 medicine is part of the picture
Frequently asked questions
Can insulin resistance be reversed?
Usually, yes — through fat loss, training and sleep. The DiRECT trial reversed established type 2 diabetes in nearly half of participants through weight loss alone.
What is the earliest test?
Fasting insulin, or HOMA-IR. These rise years before HbA1c or fasting glucose move.
Is insulin resistance only about carbohydrates?
No. Visceral fat, inactivity and sleep loss are the main drivers; carbohydrate quality matters, but cutting carbs without losing fat or training rarely fixes it.
Want this applied to your own numbers?
Fifteen minutes of intake, your labs, a human-reviewed protocol within about 24 hours, three documents, a free coach call and check-ins through the cycle. €399, follow-up included.
Build my protocol Book a 15-minute call