What Is Insulin Resistance — And Why Your Doctor Might Be Missing It

Insulin is a hormone produced by the pancreas. Its primary job is to move glucose from the bloodstream into your cells to be used as energy. When you eat, blood glucose rises, insulin is released, cells absorb the glucose, and insulin returns to baseline. Under normal conditions, this cycle is efficient and self-regulating.

Insulin resistance occurs when cells stop responding normally to insulin's signal. The pancreas compensates by producing more insulin. Over time, this compensation becomes chronic — the body requires progressively higher insulin levels to accomplish the same task. The result is hyperinsulinemia: chronically elevated insulin circulating in the bloodstream.

The critical point is this — hyperinsulinemia does most of its damage long before glucose rises. Standard glucose testing catches the downstream consequence. Fasting insulin measures the upstream driver. By the time fasting glucose is elevated, insulin resistance has often been present for years.

Consider this real-world example. A lean, active individual — under 10% body fat, training consistently, no alcohol use — gets routine bloodwork and comes back with elevated ALT and AST. Liver enzymes. The kind of result associated with fatty liver disease. No obesity. No obvious risk factors. Just a hard, distended belly that never responded to diet or training — and lab values that told a story the mirror could not. That individual was me.

Every person has a personal fat threshold: a genetically determined limit to how much fat their subcutaneous adipose tissue — the fat stored safely beneath the skin — can hold. This limit varies significantly between individuals. Some can expand their subcutaneous fat stores considerably before reaching capacity. Others reach their threshold at relatively low body fat levels.

When subcutaneous fat cells approach maximum capacity, they become hypertrophic — overgrown and inflamed. They begin to fail at their primary job. Instead of safely storing energy, they release stored lipids back into the bloodstream as free fatty acids. This is called lipid spillover, or ectopic fat deposition.

Once spillover begins, circulating free fatty acids are deposited where they should not be: the liver (producing MASLD, formerly non-alcoholic fatty liver disease), the pancreas (impairing insulin-producing beta cells), the heart (pericardial and epicardial fat), and the deep abdominal cavity (visceral fat — the hard, metabolically active fat surrounding the organs). This cascade explains why a lean, active person can develop fatty liver, metabolic syndrome, and hormonal disruption. It is not about total body fat. It is about whether you have exceeded your personal threshold for safe fat storage.

Once visceral fat accumulates through lipid spillover, it does not simply sit there. It functions as an inflammatory endocrine organ — actively secreting pro-inflammatory cytokines including IL-6 and TNF-α directly into the portal vein, which leads immediately to the liver. This is the primary driver of insulin resistance and metabolic syndrome progression.

The downstream consequences are predictable. Triglycerides rise as the liver exports excess fat into circulation. HDL falls. Blood pressure climbs. Fasting glucose eventually rises — but again, this is often the last domino, appearing years after the inflammatory and hormonal damage has already begun.

On the hormonal side, visceral fat contains high concentrations of aromatase — the enzyme that converts testosterone into estradiol. As visceral fat accumulates, aromatase activity rises, and testosterone declines as a direct result. Chronically elevated insulin suppresses sex hormone-binding globulin (SHBG), further altering biologically available testosterone. And systemic inflammatory cytokines generated by visceral fat directly suppress LH secretion from the pituitary, compounding the disruption at yet another level.

This is why many men with metabolic dysfunction experience hormonal decline that resembles primary hypogonadism — but resolves when the metabolic environment is corrected. Treating the testosterone without addressing the root cause treats a symptom while the underlying damage continues.

Standard metabolic panels are designed to catch disease, not prevent it. Here is what provides a more meaningful early picture.

Fasting insulin — the most sensitive early marker of insulin resistance. Optimal is below 7 µIU/mL. Most standard lab reference ranges do not flag anything abnormal until 20–25 µIU/mL. That gap represents years of potential silent damage.

HOMA-IR — calculated from fasting glucose and fasting insulin together. Reflects overall insulin resistance. Optimal is below 1.5. Triglyceride-to-HDL ratio — available on any standard lipid panel. A ratio above 3.0 is a strong surrogate marker for insulin resistance that most people already have the data to calculate.

Waist circumference — greater than 40 inches in men or 35 inches in women signals visceral adiposity regardless of overall weight or BMI. This measurement matters even in lean individuals who have exceeded their personal fat threshold. ALT and AST — elevated liver enzymes without an obvious cause are a metabolic signal worth taking seriously, not dismissing as exercise artifact.

Metabolic disease does not begin with a diagnosis. It begins years earlier — with hyperinsulinemia, a personal fat threshold exceeded, lipid spillover into organs, and a cascade of inflammatory and hormonal disruption that standard bloodwork is not designed to catch early.

The most important first step is measuring what actually matters. Ask your provider to add a fasting insulin level to your next bloodwork. If that number is above 7, you have meaningful information — and a starting point for a conversation that most medical appointments never reach.

In the next post, we cover what actually moves the needle — including GLP-1 receptor agonists like semaglutide and tirzepatide, the peptide MOTS-c which restores mitochondrial metabolic flexibility at the cellular level, and the GHRH and GHRP combinations that target visceral fat directly while preserving the muscle mass that makes metabolic correction last.