The body can produce the amount of glucose it needs through converting proteins using Gluconeogenesis. Dietary intake of carbohydrates/glucose is not necessary.
I don't think you went over that medical summary I provided: Fatty acids do not serve as fuel for the brain, because they are bound to albumin in plasma and so do not traverse the blood-brain barrier. In starvation, ketone bodies generated by the liver partly replace glucose as fuel for the brain.
There is almost zero risk not getting enough sugar these days. That's not something to worry about.