Insulin Resistance & Visceral Fat
How a compromised gut drives a damaged metabolism — and from there, most modern Western disease
Insulin resistance (IR) occurs when cells stop responding properly to insulin, forcing the body to produce ever-higher levels to keep blood glucose stable. A key — and often overlooked — upstream trigger is gut dysbiosis and intestinal permeability (leaky gut): when the gut wall is compromised, bacterial endotoxins enter the bloodstream, driving the insulin signalling dysfunction that follows. Critically, this can occur in people who appear to eat well; the gut wall can be damaged by antibiotics, chronic stress, environmental toxins, and other factors independent of diet quality.
Chronically elevated insulin directs excess energy into storage — specifically as visceral fat, the deep abdominal fat surrounding the organs. Unlike subcutaneous fat (under the skin), visceral fat is metabolically active. It secretes pro-inflammatory molecules — including interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) — directly into the portal circulation, driving systemic inflammation. This chronic low-grade inflammation is the upstream mechanism behind most major Western chronic diseases, from type 2 diabetes and cardiovascular disease to Alzheimer's, fatty liver disease, and hypertension.
How To Find Out If You Have Insulin Resistance
Two straightforward tests can identify insulin resistance. Neither is part of a standard NHS or US doctor blood panel — but both are accessible.
HOMA-IR
The Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) measures both fasting glucose and fasting insulin to calculate your level of insulin resistance directly. It is the most precise available marker. In the UK, order privately through Vitall — a nurse comes to your home to take the samples.
Order HOMA-IR Test →TG/HDL Ratio
The Triglycerides to High-Density Lipoprotein (TG/HDL) ratio is a reliable proxy for insulin resistance. Both values appear on a standard lipid panel — request one from your NHS GP, or from your doctor in the US. Divide your triglycerides figure by your HDL figure. A ratio above 2.0 (US mg/dL units) or 0.87 (UK/EU mmol/L units) is a strong signal of insulin resistance.
Supporting Research
Four peer-reviewed studies supporting the role of visceral fat as the primary inflammatory driver of metabolic disease.
Researchers drew blood simultaneously from the portal vein (which drains visceral fat) and the radial artery in 25 extremely obese patients during gastric bypass surgery. They found that IL-6 — a key inflammatory molecule — was approximately 50% higher in portal vein blood than in arterial blood, and that this correlated directly with systemic C-reactive protein levels. This directly supports the idea that visceral fat is actively secreting inflammatory signals into the bloodstream, providing a plausible mechanism for how it drives systemic inflammation and insulin resistance, rather than being a passive bystander.
https://pubmed.ncbi.nlm.nih.gov/17287468/Using MRI to measure fat depots directly, this study found that visceral fat — independently of BMI or subcutaneous fat — was associated with triglyceride-rich lipoproteins and inflammation in both adults and adolescents. The metabolomic profile of visceral fat closely resembled profiles that predict type 2 diabetes (R²=0.88 in adults) and myocardial infarction, but not ischemic stroke. The finding that these associations appear even in normal-weight individuals and in adolescents is particularly striking — suggesting visceral fat accumulation may be setting the stage for metabolic disease long before conventional obesity markers raise any alarm.
https://www.nature.com/articles/s43856-022-00140-5This comprehensive review contrasts "metabolically healthy obese" (MHO) individuals — who have elevated subcutaneous fat but without excessive visceral fat accumulation — against "metabolically unhealthy obese" (MUHO) individuals, who exhibit elevated insulin resistance and systemic inflammation. The authors conclude that visceral adiposity is strongly associated with insulin resistance, atherogenic dyslipidemia, hypertension, and non-alcoholic fatty liver disease — the full cluster now recognised as metabolic syndrome. The distinction is directly relevant: it is not how much fat a person carries overall, but where it sits, that determines metabolic risk.
https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2020.00022/fullIn a cross-sectional and longitudinal study of nearly 6,000 normal-weight participants, visceral fat area — measured by CT scanning — emerged as a key factor in metabolic syndrome development. The researchers identified that visceral fat drives insulin resistance via inflammatory cytokines including TNF-α and IL-6, which impair insulin receptor signalling through specific kinase pathways. The fact that this was observed even in normal-weight individuals underscores a key point: visceral fat and the inflammation it generates can be present and harmful even when a person looks outwardly lean.
https://pmc.ncbi.nlm.nih.gov/articles/PMC11837645/