Brain Fuel Ketones... Fuel metabolism in starvation (George F Cahill)

Brain substrate utilization in three fasting obese volunteers after several weeks of starvation switches from 100% Glucose to 70% Ketones. 

"Many studies suggest human brain cells can survive with little to no glucose, but proving the point is difficult as well as experimentally difficult and ethically questionable."

And also interesting:

"Not well known, however, is the metabolism of the human newborn, which is essentially ketotic. Blood glucose levels fall strikingly in the neonate, and con- centrations of βOHB may rise to 2–3 mM. The newborn human brain consumes 60%–70% of total metabolism at birth, nearly half via β-hydroxybutyrate. Fitting in with this pattern is maternal colostrum. It contains much triglyceride and protein, but little lactose, starting man’s entry into society on an Atkins diet (Figure 6)!"