Visceral adipose tissue surrounds the organs in the abdominal cavity. Distinct from subcutaneous fat in metabolic activity, inflammatory signaling, and disease association.
Mechanism — Secretes pro-inflammatory cytokines (IL-6, TNF-alpha), drains directly to the liver via the portal vein, drives insulin resistance, and promotes systemic inflammation. Highly responsive to caloric deficit and exercise.
Use case — Measure via DEXA scan (most accurate), MRI, or waist circumference proxy. Target: less than 100 cm² VAT in men, less than 80 cm² in women. Reduces faster than total fat with diet + Zone 2 + resistance training.
Caveats — Waist circumference is the cheapest screen — under 40 inches (men) and 35 inches (women) is the screening threshold. Skinny-fat: normal BMI with high visceral fat — equally dangerous.