This might sound weird but I just found some reports claiming that fasting triggers the brain to create BDNF:

http://www.drmirkin.com/public/ezine022612.html

And here you have this guy claiming that fasting and exercise done PROPERLY can even do a better job:

http://articles.mercola.com/sites/ar...lly-young.aspx

though I realize that this Mercola guy is a bit fishy. This is a study about exercise and release of BDNF in human brain:

http://ajpregu.physiology.org/conten....2009.full.pdf