Ectopic fat

Ectopic fat is fat stored in or around organs that normally hold very little of it. Think liver, muscle, pancreas, and heart. It is different from the fat under your skin or around your belly organs. Here is how it builds up. When you eat more than your under-skin fat can store, fat spills into these organs. There it forms toxic byproducts (diacylglycerol, or DAG, and ceramides) that jam insulin signaling. In the liver, DAG switches on an enzyme (PKC-ε) that blunts the insulin signal and makes the liver overproduce glucose. In muscle, a related enzyme (PKC-θ) cuts glucose uptake. And in the pancreas, fat buildup blunts the first burst of insulin. Roy Taylor named the 'personal fat threshold': each person has a genetically set storage limit, and past it, ectopic fat starts, regardless of body weight. The 2023 ReTUNE study tested this in normal-weight people with type 2 diabetes. A median 6.5% weight loss normalized liver fat, restored β-cell function, and put 70% into remission. Shulman's 2014 NEJM review built the framework linking ectopic fat to insulin resistance in humans (using MR spectroscopy). The causal direction is supported by intervention and genetic (Mendelian randomization) studies, though some observational links stay confounded. You can measure it by MRI, MR spectroscopy, or CT, and it adds risk information beyond BMI or waist size, even at a normal weight.

Last reviewed: June 22, 2026

This definition is educational and is not medical advice, a diagnosis, or treatment. Talk to a doctor about any health decisions. Read our full medical disclaimer