SAMA HOOLE: The heart runs on fat, and the organ they put on a low-fat diet is the one organ in the body that eats almost nothing else.

The heart runs on fat, and the organ they put on a low-fat diet is the one organ in the body that eats almost nothing else. Every heartbeat is paid for, and the currency is fatty acids. They supply the bulk of the heart's energy, around the clock, from the day you are born. Heart muscle is a third mitochondria by volume, more than any other muscle in the body, and mitochondria are where fat is burned. A heart cell burns fat at rest, burns fat under load, and burns fat while you sleep. Given a choice between glucose and fat, the heart takes the fat. Given ketones, it takes those more readily still, and gets more work out of every unit of oxygen. A failing heart, when it starts to run out of road, switches more of its fuel to ketones. The sick heart reaches for the thing the diet sheet forbade. The cardiologist's own ward uses that. Fasting patients, patients in ketosis, patients on fat, and the heart keeps time. Then the same ward hands the patient a diet sheet with the fat cut off and the bread left on, in the name of the heart. The organ they are protecting from fat is the one organ that was built to live on it. Heart-healthy is a word for food the heart would not choose.

— Sama Hoole (@SamaHoole) October 25, 2026

The heart runs on fat, and the organ they put on a low-fat diet is the one organ in the body that eats almost nothing else. Every heartbeat is paid for, and the currency is fatty acids. They supply the bulk of the heart's energy, around the clock, from the day you are born. Heart muscle is a third mitochondria by volume, more than any other muscle in the body, and mitochondria are where fat is burned. A heart cell burns fat at rest, burns fat under load, and burns fat while you sleep. Given a choice between glucose and fat, the heart takes the fat. Given ketones, it takes those more readily still, and gets more work out of every unit of oxygen. A failing heart, when it starts to run out of road, switches more of its fuel to ketones. The sick heart reaches for the thing the diet sheet forbade. The cardiologist's own ward uses that. Fasting patients, patients in ketosis, patients on fat, and the heart keeps time. Then the same ward hands the patient a diet sheet with the fat cut off and the bread left on, in the name of the heart. The organ they are protecting from fat is the one organ that was built to live on it.

Heart-healthy is a word for food the heart would not choose.