BDNF is essential for learning and memory; its 50% reduction in mice causes overeating, obesity, and impaired learning.

“It is the most heavily studied such nerve cell growth factor in the brain. And it is essential for learning and memory. You can't knock out the BDNF gene in mice. They'll die. You can reduce levels genetically and then that will impair learning and memory. Actually, interestingly, if you reduce levels of BDNF by about 50%, the animals will overeat and become obese.”