Have you ever wondered why cannabis makes you hungry?

Also known as “the munchies”, the phenomenon is so common it has seeped its way from many a dark, smoky bedroom through to the big screen — inspiring scenes in everything from the films of Cheech and Chong to the Ted series starring Mark Wahlberg.

But despite the humorous depiction of the munchies on film, hunger can be a serious and powerful side effect of cannabis use.

The term “munchies” is said to have been first noted in the famous study on ‘being stoned’ by Charles T Tart in 1971, in which the mental state of 150 marijuana users was observed.

More recently though, research has focused on the neurological processes behind the munchies. Scientists believe the munchies effect is caused by the psychoactive component of cannabis, Tetrahydrocannabinol (THC), and its interaction with cannabinoid receptors in the brain — mostly with a receptor known as CB1.

Research from 2014 suggests that people eat more food after using weed because they smell and taste it more intensely. The study, published in Nature Neuroscience, found that THC fits into CB1 receptors in the brain’s olfactory bulb.

Tests conducted on mice showed that THC heightened the rodent’s sense of smell, increased their hunger and gave them the munchies.

A 2014 study showed one of these mechanisms involves increasing your ability to smell.  THC binds to receptors in your main olfactory bulb (MOB).  The authors stated, “Local pharmacological and genetic manipulations revealed that endocannabinoids and exogenous cannabinoids increased odor detection and food intake in fasted mice by decreasing excitatory drive from olfactory cortex areas to the MOB”.

The increased ability to smell also simultaneously makes your food taste better.  This is because as you chew, you tend to force air through your nasal passages.  This carries the smell of food with it and you’re able to grasp more complex flavors.  If you didn’t have this smell-taste combination, you’d be limiting your taste sensations to the ones produced by chemicals alone.  Those would be salty, sour, sweet, bitter, and umami.

THC also increases hunger by affecting previously mentioned receptor site CB1. Once attached, it increases the palatability of sucrose, but has no effect on the sensations of salty or bitter.  This could help explain the subjective feeling that sweet foods taste better when high.  CB1 also has the ability to produce dopamine in an area of your hypothalamus called your nucleus accumbens.

Similar receptor sites in the hypothalamus also get stimulated by THC and cause the release of the hormone ghrelin.  Ghrelin acts on the hypothalamus to increase hunger and at the same time, helps prepare your GI tract for food intake.  It does this by increasing gastric acid production and motility.  Basically digesting and moving food through your GI tract faster.