Again, the important thing is ATP, and you can get it from either glucose or ketone bodies:

> In fact, the late George Cahill did an experiment many years ago (probably would never get IRB approval to do such an experiment today) to demonstrate how ketones can offset glucose in the brain. Subjects with very high levels of B-OHB (about 5-7 mM) were injected with insulin until glucose levels reached 1 mM (about 19 mg/dL)! A normal person would fall into a coma at glucose levels below about 40 mg/dL and die by the time blood glucose reached 1 mM. These subjects were completely asymptomatic and 100% neurologically functional.

https://peterattiamd.com/ketosis-advantaged-or-misunderstood...