The science behind munchies: marijuana and your appetite

We all know that marijuana is a popular recreational drug- and that it’s also got a variety of medicinal uses, including reducing nausea and boosting appetite. But what, exactly is marijuana - and how does it affect the appetite and digestive system?
The answer to that first question is pretty simple, so let’s start with that. The term ‘marijuana’ refers to several plants in the cannabis genus, including sativa, indica, and ruderalis.
Doctors typically prescribe marijuana to treat inflammatory, gastrointestinal, and cognitive ailments. Marijuana is also frequently administered to cancer patients, since it helps ease the pain associated with chemotherapy while increasing the patient’s appetite. This is why marijuana is used in an effort to minimize weight loss, which could lead to further health complications.
As you can imagine, this increase in appetite is one of marijuana’s most well-known effects, you might refer to it as “the munchies”. In fact, historical sources confirm that people as early as 300 BCE knew that cannabis stimulates appetite, and noted how these cravings were for sweet and savory food. Let’s dig into why that happens.

How marijuana works

One of the main active ingredients in marijuana - a chemical compound known as tetrahydrocannabinol (THC) - is one of the main culprits responsible for “the munchies”. Once the marijuana is consumed (normally by smoking), THC activates a receptor called cannabinoid receptor type 1 (CB1), which helps increase appetite. CB1 is also involved with the receptor for ghrelin, a hormone that contributes to an increase in the sensation of hunger.
CB1 receptors appear in a variety of different areas of the body. In each of these areas, these CB1 receptors act in slightly different ways - and many of those effects help increase the desire to eat. CB1 receptors are found in all of the following areas:

• The hypothalamus and rhombencephalon, two sections of the brain that help regulate food intake.
• The basal ganglia, where they may help enhance the pleasure we get from eating.
• The stomach and the small intestine, which also secrete ghrelin, speeding up digestion.
• The limbic forebrain, where they may also influence the palatability of food.

Researchers have found that inhaling cannabis is also associated with lower levels of peptide tyrosine tyrosine (PYY), a peptide that contributes to appetite suppression. People who use marijuana recreationally tend to have increased levels of ghrelin and decreased levels of PYY, which may be one reason why their daily caloric intake tends to be greater.
Studies have also shown that a person’s method of THC consumption (oral capsules, smoke inhalation, or suppository) can influence their food choice, as well as their overall food consumption. For example, study participants who took a suppository consumed significantly more calories throughout the day than participants who took an oral capsule.
Recent research on CB1 has revealed that a synthetic form of THC (dronabinol) can activate a subset of neurons called proopiomelanocortin neurons (POMC). Though POMC are usually responsible for the feeling of fullness after a meal, these neurons can either release hormones that suppress hunger, or hormones that increase appetite. When CB1 is activated, these hormones prevent POMC from suppressing hunger, and enable it to start increasing your appetite.

Suppressing appetite through the CB1 receptor

Since activating the CB1 receptor contributes to an increase in appetite, blocking it has the opposite effect. Studies on individual cells show that blocking CB1 receptors significantly increases production of adiponectin, a hormone with anti-inflammatory effects and a negative correlation with obesity.
Researchers have also used compounds that can block the CB1 receptor - which are known as endocannabinoid antagonists - to treat obesity associated with eating disorders, which is characterized by compulsive binge eating or cravings for sweets and snacks. Animal studies show that rats given rimonabant, an endocannabinoid antagonist anti-obesity drug, experience weight loss and reduced levels of blood insulin.
Still, a lot more research is needed before we can start recommending these kinds of therapies to human patients. The CB1 drug Rimonabant, for example, failed to earn approval from the U.S. Food and Drug Administration (FDA) - and it’s no longer sold in Europe either, due to side effects associated with its use, which include severe depression and suicidal thoughts. Since CB1 receptors are found all throughout the body, it is difficult to pinpoint the cause of these side effects.
Future endocannabinoid antagonists, however, may play a role in treating obesity by blocking CB1 receptors, increasing adiponectin production, and reducing appetite.
Marijuana has been a part of our society longer than any one civilization, and researchers continue to paint a more complete picture of the compound with every passing year. Follow-up studies will not only need to investigate CB1’s effects throughout the body, but also the different ways THC functions when ingested in various ways. More research on marijuana may also lead to breakthroughs in the fight against obesity because of how effective manipulating hunger can be when it comes to controlling our daily caloric consumption.