Fact, The reason that cannabis gives you munchis is because
of Endocannabinoids, which are the chemicals in the brain that
seem to control appetite and actually make food more apealing.
These are chemicals already in your anatomy but cannabis increases
these upon smoking or ingesting marijuana. There is actually a study
on how to block these chemicals because they are more prevalent
in obese people, there is a drug out called Rimonabant which blocks the Endocannabinoids. They are using this as a weight loss drug in some countries
now.