Fasting does good things for the brain, and this is evident by all of the beneficial neurochemical changes that happen in the brain when we fast. It also improves cognitive function, increases neurotrophic factors, increases stress resistance, and reduces inflammation.

Fasting is a challenge to your brain, and your brain responds to that challenge by adapting stress response pathways which help your brain cope with stress and risk for disease. The same changes that occur in the brain during fasting mimic the changes that occur with regular exercise. They both increase the production of protein in the brain (neurotrophic factors), which in turn promotes the growth of neurons, the connection between neurons, and the strength of synapses.

“Challenges to your brain, whether it’s intermittent fasting [or] vigorous exercise . . . is cognitive challenges. When this happens neuro-circuits are activated, levels of neurotrophic factors increase, that promotes the growth of neurons [and] the formation and strengthening of synapses. . . .” 

Fasting can also stimulate the production of new nerve cells from stem cells in the hippocampus. He also mentions ketones (an energy source for neurons), and how fasting stimulates the production of ketones and that it may also increase the number of mitochondria in neurons. Fasting also increases the number of mitochondria in nerve cells; this comes as a result of the neurons adapting to the stress of fasting (by producing more mitochondria).

By increasing the number of mitochondria in the neurons, the ability for nerons to form and maintain the connections between each other also increases, thereby improving learning and memory ability.

“Intermittent fasting enhances the ability of nerve cells to repair DNA.”

http://www.collective-evolution.com/2015/12/11/neuroscientist-shows-what-fasting-does-to-your-brain-why-big-pharma-wont-study-it/