Study: Marijuana-like substances control appetite

By The Associated Press

Scientists have found that marijuana-like substances naturally produced in the brain stimulate appetite — a finding that not only offers clues to treating obesity but also explains why pot smokers get the "munchies."

The study suggests that these endocannabinoids are part of the brain's complex system for controlling when and how much to eat.

Scientists have known for several years about the existence of these substances, which are chemically similar to the active ingredient in marijuana but do not make people high. However, their exact role in the brain was unclear.

In a study in Thursday's issue of the journal Nature, researchers found that mice that had been genetically altered so they could not respond to endocannabinoids ate less than normal mice did. The mice lacked "receptor" structures that endocannabinoids activate in the brain.

And when ordinary mice were given a substance that blocked endocannabinoids from acting at these receptors, they ate less than normal as well.

The findings help explain why marijuana users get a ravenous hunger — the "munchies" — after smoking pot.--