Carbohydrates are actually the one macronutrient that the body can do without. There are three macronutrients: carbohydrates, protein and fat. The body needs protein and it needs fat. It also needs glucose, but in the absence of dietary carbohydrates, the body will produce glucose in the liver.
When the body becomes fat-adapted, it has changed its primary source of fuel from glucose back to fat (yes – ‘back to’ – because we are born in a state of ketosis). All of the vital organs in the body actually prefer to use fat for fuel.