Metabolic Syndrome

Metabolic syndrome is a clustering diagnosis rather than a disease in its own right. You meet criteria with three or more of: waist circumference above the ethnicity-specific threshold, triglycerides at or above 1.7 mmol/L, HDL below 1.0 mmol/L in men or 1.3 in women, blood pressure at or above 130/85, and fasting glucose at or above 5.6 mmol/L — or being treated for any of these. The reason to group them is that they share a root. Visceral adiposity and insulin resistance drive all five, which is why they cluster far more often than chance would predict and why a single intervention improves several at once. Visceral fat is metabolically active tissue: it releases free fatty acids directly into the portal vein, secretes inflammatory cytokines including IL-6 and TNF-alpha, and drives hepatic overproduction of triglyceride-rich VLDL particles. That VLDL overproduction explains the characteristic lipid pattern — high triglycerides with low HDL and small dense LDL particles, which are more atherogenic than the LDL number alone suggests. The clinical consequence is substantial. Metabolic syndrome roughly doubles the risk of cardiovascular disease over five to ten years and increases type 2 diabetes risk approximately fivefold. It is also the metabolic backdrop for non-alcoholic fatty liver disease, obstructive sleep apnoea, PCOS and gout. The encouraging side of a shared root is that it responds to shared treatment. Weight loss of 7-10% improves all five components simultaneously, and exercise improves triglycerides, HDL, blood pressure and glucose independently of weight change.

• •Increased waist circumference — often the only visible sign
• •Skin tags and acanthosis nigricans
• •Fatigue, particularly after meals
• •Raised blood pressure, usually asymptomatic
• •Snoring and unrefreshing sleep from associated sleep apnoea
• •Often entirely silent until a complication appears

• •Visceral and hepatic fat accumulation
• •Insulin resistance
• •Physical inactivity and low muscle mass
• •High refined carbohydrate and sugar-sweetened drink intake
• •Obstructive sleep apnoea, which worsens insulin resistance independently
• •Chronic sleep restriction
• •Genetic predisposition and ethnicity
• •Ageing and, in women, the menopausal transition
• •Medications including corticosteroids and atypical antipsychotics

The unifying mechanism is ectopic fat and the insulin resistance it produces. When subcutaneous adipose tissue reaches its individual storage capacity, lipid overflows into the visceral compartment, liver and muscle. Visceral fat drains directly into the portal circulation, exposing the liver to a high flux of free fatty acids that drives gluconeogenesis, VLDL production and hepatic insulin resistance. From there each criterion follows. Hepatic VLDL overproduction raises triglycerides. Cholesteryl ester transfer protein activity, driven by that triglyceride excess, depletes HDL and generates small dense LDL. Hyperinsulinaemia promotes renal sodium retention and sympathetic activation, raising blood pressure. Impaired muscle glucose uptake and unsuppressed hepatic glucose output raise fasting glucose. Low-grade chronic inflammation runs through all of it. Adipose tissue macrophage infiltration produces the cytokine profile that impairs insulin signalling further, creating a self-reinforcing loop. The personal fat threshold concept matters here: the amount of fat that triggers this cascade varies widely between individuals and between ethnic groups, which is why South Asian populations meet criteria at considerably lower waist circumferences than European populations.