The hypothalamus is a tiny part of the brain that controls messages among the gut, fat cells and the brain. It tells us when we are hungry and when we have had enough to eat. 

Hypothalamic obesity (HyOb) is a complicated medical condition that can occur from the growth of rare brain tumors and from other types of injury to the hypothalamus. Craniopharyngioma (krā'nē-ō-fə-rĭn'jē-ō'ma) is one of the tumors that can cause HyOb.