Study: What's Behind the Munchies?

Whether one smokes pot or not, the notion of the "munchies" is part of the almost-universal marijuana consciousness.

It's that insatiable desire to eat something, be it chocolate or potato chips, after smoking or eating food containing the drug.

Researchers now say that this strong desire to eat comes from natural chemicals in pot — cannabinoids — that are similar to chemicals in the human brain that help regulate body weight.

Cannabinoids Induce Hunger

The investigators say, in a study appearing in the current issue of Nature, cannabinoids are one of two key chemicals that help control hunger in the brain. Cannabinoids and the hormone leptin help regulate the body's supply of energy through the intake of food.

"They have opposite effects," said Dr. George Kunos, science director at the National Institute of Alcohol Abuse and Alcoholism at the National Institutes of Health in Bethesda, Md., and one of the study's authors. "The cannabinoids make us hungry while the leptins make us satiated. As the concentration of one increases, the concentration of the other decreases."

Smoking marijuana adds more of the hunger-inducing cannabinoids to the already natural supply that exists in the brain. This increased supply leads to a heightened desire to eat, even when extra energy is not actually needed by the body.

Mice Designed to Not Get 'Munchies'

The researchers came to their conclusion using mice genetically engineered to lack the brain receptors for these natural cannabinoid molecules. Without the receptors, the molecules have nothing to attach to on the surface of brain cells and thus are unable to cause hunger.

"In the mice lacking the cannabinoid receptors, they ate less even though they had been given less food beforehand to make them naturally hungry," Kunos said. "This confirms the role these natural molecules play in hunger and body weight.

"This research is important because it shows a whole other component of food intake and body weight and may provide new targets in the brain for potential therapeutic intervention for such diseases as anorexia or obesity."

In addition to hunger, Kunos said natural cannabinoids in the body have also been linked to reducing blood pressure, dilating and contracting lung tissues in asthma, motor function, and may even be related to alcohol consumption, the topic of his current research.

An international team of researchers from Virginia, Seattle, Italy and Japan participated in this study.

Scott Terranella is a third-year medical student at Emory University in Atlanta, and a news editor in the ABCNEWS Medical Unit.