What causes the acetone breath seen in type 1 diabetes?

In type 1 diabetes, the body is unable to produce insulin, which is a hormone that helps glucose (sugar) from the blood to enter the cells for energy. Without insulin, blood sugar levels can get dangerously high, and the body begins to break down fat and muscle for energy. This process, called ketosis, produces ketones, which are acidic waste products that can build up in the blood and cause ketoacidosis, a serious complication of type 1 diabetes. Acetone is one of the ketones that can be excreted in the breath, giving it a distinct, fruity odor.