Visceral adiposity and peptides — what the literature actually supports for the deep-fat depot

Why this dossier exists

The single most important framing in metabolic medicine that BMI obscures is the distinction between subcutaneous fat — the storage compartment under the skin, on the hips, thighs, and abdominal wall — and visceral adipose tissue (VAT), the metabolically active depot that wraps around the liver, pancreas, intestines, and mesentery. Two adults at BMI 28 can carry an order-of-magnitude difference in cardiometabolic risk depending on which depot dominates. The "thin-outside, fat-inside" phenotype (TOFI) is the canonical demonstration: metabolically-obese normal-weight prevalence runs roughly 20–27% in pooled meta-analyses, and a meaningful subset of nominally lean adults carry a high-VAT body composition that follows the same insulin-resistance, dyslipidemia, and atherosclerosis trajectory as classically obese adults (Tchernof and Després, Physiol Rev 2013, 93(1):359–404). The inverse — metabolically healthy obesity, where high BMI sits with low VAT and preserved markers — defines roughly 7% of the obese population in the same literature.

VAT is not merely fat in an inconvenient location. Visceral adipocytes secrete more inflammatory cytokines (TNF-α, IL-6, MCP-1) and pro-thrombotic PAI-1, and less adiponectin per gram than subcutaneous adipocytes; they drain directly through the portal vein into the liver, producing the first-pass exposure that links visceral adiposity to hepatic insulin resistance, MASLD, and dyslipidemia in a way subcutaneous fat does not (Hocking et al., Endocr Rev 2013, 34(4):463–500). The 2019 International Atherosclerosis Society position statement codified the framing: VAT measured by CT or MRI is an independent risk marker for cardiovascular and metabolic morbidity, and ectopic-fat deposition in liver, pericardium, and pancreas drives the residual risk BMI fails to capture (Neeland et al., Lancet Diabetes Endocrinol 2019, 7(9):715–725).

The editorial center is tesamorelin — the only peptide with an FDA-approved label for VAT reduction and the only peptide whose mechanism is preferentially lipolytic at the visceral depot rather than weight-loss-mediated. The GLP-1 / GIP / glucagon-receptor incretin class produces VAT reduction that is substantial in magnitude but largely proportional to total weight loss. The GH-secretagogue class outside tesamorelin operates on the same axis in theory but has thinner controlled-trial evidence on VAT specifically. AOD-9604 and 5-Amino-1MQ sit at the speculative-and-failed end. The hepatic-fat decision guide covers the ectopic-liver-fat depot that travels with VAT; this dossier covers the upstream visceral depot.