Decoded: How brain controls hunger

Although hunger is essential for survival, abnormal hunger can lead to obesity and eating disorders that are now reaching near-epidemic proportions around the world. The solution lies somewhere deep inside your brain.

To unlock the mystery behind hunger pangs, researchers are creating a wiring diagram of the complex brain circuits that regulate the intense urge to munch in office or rush for refrigerator in night.

"Our goal is to understand how the brain controls hunger," explained Bradford Lowell, an investigator with Massachusetts-based Beth Israel Deaconess Medical Center's (BIDMC) division of endocrinology, diabetes and metabolism.

Abnormal hunger can lead to obesity and eating disorders, but in order to understand what might be wrong - and how to treat it - you first need to know how it works, added Lowell, also professor of medicine at Harvard Medical School.

The findings show that Agouti-peptide (AgRP) expressing neurons - a group of nerve cells in the brain's hypothalamus - are activated by caloric deficiency.

When AgRP was either naturally or artificially stimulated in animal models, it caused mice to eat voraciously after conducting a relentless search for food.

The hunger-inducing neurons that activate these AgRP neurons are located in the paraventricular nucleus - a brain region long thought to cause satiety, or feelings of fullness.

"This unexpected finding adds an important dimension to our understanding of what drives appetite," said Lowell.

To deal with this particularly complex brain region, the Lowell team is taking a step-by-step approach to find out how the messages indicating whether the body is in a state of feeding or fasting enter this system, said the study that appeared in the journal Nature.

"We are getting closer and closer to completing our wiring diagram. The nearer we come to understand how it all works, the better our chances of being able to treat obesity and eating disorders - the consequences of abnormal hunger," explained Lowell.