Fatty Liver.

The liver following orders.

For a condition affecting a third of adults, fatty liver is remarkably little discussed. Part of the reason is that it rarely announces itself — it's usually found by accident, on a scan or blood test done for something else. And part is historical: it was named for what it is not ("non-alcoholic"), which quietly obscured what it is.

From NAFLD to MASLD.

Fatty liver means fat accumulating inside liver cells — steatosis — beyond a small normal amount. For decades it was called NAFLD, non-alcoholic fatty liver disease, defined by excluding alcohol. In 2023 an international consensus renamed it MASLD — metabolic dysfunction-associated steatotic liver disease — precisely to say out loud what it is: a liver condition tied to metabolic dysfunction, diagnosed by what it is (fatty liver plus a metabolic feature such as raised blood sugar, blood pressure or waist) rather than by what it is not.[2]

The rename matters more than it sounds. "Non-alcoholic" framed the disease around a thing the patient wasn't doing. "Metabolic dysfunction-associated" names the actual driver — and points, correctly, at the fire.

The paradox at the heart of it.

Here is the mechanism the insulin chapter flagged as its strangest, and it explains fatty liver exactly. Insulin resistance in the liver is selective: the pathway by which insulin should tell the liver to stop releasing glucose becomes resistant — so the liver keeps pouring out glucose — while the pathway by which insulin drives fat-making stays fully sensitive, and is now being driven hard by the high insulin.[4]

Why fructose earns a special mention.

Not all carbohydrate reaches the liver equally. Fructose — half of table sugar, and much of the sugar in sweetened drinks — is metabolised largely in the liver, and it feeds de novo lipogenesis particularly directly, while bypassing some of the normal appetite and insulin signals that limit glucose. This is why sugary drinks and high-fructose loads are so closely tied to fatty liver: they deliver fat-making substrate straight to the organ that makes the fat.[1]

Why it matters.

For most people fatty liver stays at the quiet stage — simple steatosis — and does little for years. But in a proportion it progresses: the fat-laden liver becomes inflamed (now called MASH, formerly NASH), and sustained inflammation drives fibrosis — scarring — which over time can reach cirrhosis and its serious complications. Fatty liver is also an independent marker of cardiovascular risk, travelling with the rest of the metabolic cluster.

Because a large share of the fat is made by the liver from carbohydrate under insulin's direction, the most on-mechanism intervention is the one that runs through the whole series: lower the insulin load — turn down the tap the liver controls.

• Reduce refined carbohydrate and concentrated fructose — turning down the de novo lipogenesis tap directly, at the substrate that feeds it.
• Lose visceral fat and improve insulin sensitivity — which reduces both the spillover into the liver and the insulin drive on fat-making; weight loss is the best-evidenced intervention for reducing liver fat.
• Move — exercise lowers liver fat even before much weight is lost, by improving insulin sensitivity and burning fuel.

The same honesty applies to the ending.

The early stage is often reversible by turning down the tap the liver controls; the late stage is not; and the difference between them is worth finding early. Not the liver failing at random — the liver following orders, and able to stop when the orders change.

Not the liver failing at random — the liver following orders, and able to stop when the orders change.