You don't. The liver can make glucose from fat, and the body can run on ketones as its primary energy source. That's the basis of the now famous "keto diet". N

You don't. The liver can make glucose from fat, and the body can run on ketones as its primary energy source. That's the basis of the now famous "keto diet". Now, I don't advocate for the keto diet, and if you indent to do that you should probably talk to a doctor, like for all restrictive diets. EDIT: I misread your statement. Of course you would die of starvation if you couldn't make glucose. But why couldn't you make glucose, assuming you don't have a specific disease preventing it.