Answer by David Wilson:

Here's a TED Talk by Mark Mattson, professor of neuroscience – the talk is about why fasting is good for the brain…and some speculation as to why…
Fasting can –
  • increase neurotrophic factors, which increase growth and strength of neurones and synapses and increase the energy production of the mitochondria of the brain
  • increase ketones, which as well as being good for epilepsy, seem to increase the energy levels in the brain
  • increase ability of nerve cells to increase rate of DNA repair
Why do these things happen? It's speculated that when food supply is short we need to boost our chances of finding some, so our brain adapts to take on the extra challenge…

Can fasting promote brain development?