Ketosis:

There are two kinds of ketosis: ketosis-lipolysis and ketosis-acidosis, and hand-wringing over ketogenic diets usually starts from confusing the two. When the body does not have any glucose available, as in a diet which eliminates carbohydrates, it manufactures another fuel from fat, and uses ketones as the fuel delivery system. To use the fat for fuel, the body breaks it down into glycerol and free fatty acids, which then break down into couplings of two-carbon compounds called ketone bodies. This is a perfectly normal state of affairs for the body. This is how it metabolizes fat. Lipolysis simply means fat burning. With sufficient intake of dietary protein, the body continues to be able to use glucose as fuel while optimally burning bodyfat.

However, in a fasting state, the body can enter ketosis-acidosis or ketoacidosis. Diabetic ketoacidosis (DKA) is a state of absolute or relative insulin deficiency, and in rare cases is fatal. Alcoholic ketoacidosis is along the same lines, but complicated by an episode of binge drinking (ethanol metabolism further reduces available glucose) combined with fasting. Non-diabetics who do not fast or regularly binge drink are not at risk.