The science of being hungry
Appetite involves the brain, stomach and hormones
“Anyone for seconds?” Your answer will depend on how tasty the first helping was, who is asking, and whether you might look ungrateful. Unconsciously, a shifting network of interactions between brain, stomach and hormones will also influence whether you still feel peckish or are completely stuffed.
Many controls on appetite affect a small part of the brain known as the hypothalamus. It responds to hormones produced by the stomach to drive hunger. Ghrelin, which is secreted when no food has arrived for a while, stimulates the hypothalamus to make you feel hungry. The secretion eases up as your stomach fills. The hypothalamus registers many other chemical signals that may tell you to eat less, as well as producing hormones of its own. It is a system with checks and balances.
There is increasing evidence that it can keep your weight fairly constant by making you hungrier if you cut your energy intake – bad news for dieters. Disruption to the appetite system helps us understand how it works. For example, one of the genetic changes in the inherited disorder Prader–Willi syndrome leads to very high ghrelin production, and children with the condition are hungry all the time.
‘Big Picture: Food and Diet’ (2011)
Photo and Share CC/Flickr CC BY