I just have to give a quote here:
And now let's really get down to the mitochondrial level. Mitochondria are the power plants of our cells, where all the energy is produced (as ATP). Now, when I was taught about biochemical fuel-burning, I was taught that glucose was "clean" and ketones were "smokey." That glucose was clearly the preferred fuel for our muscles for exercise and definitely the key fuel for the brain. Except here's the dirty little secret about glucose - when you look at the amount of garbage leftover in the mitochondria, it is actually less efficient to make ATP from glucose than it is to make ATP from ketone bodies! A more efficient energy supply makes it easier to restore membranes in the brain to their normal states after a depolarizing electrical energy spike occurs, and means that energy is produced with fewer destructive free radicals leftover.Go and read the post, its very informative plus well written. I've been for ages trying to counter that "glucose is the brains fuel" mantra of the CW gurus out there - now i can.