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Why Does Cannabis Cause the Munchies?

Munchies. If you’ve tried recreational cannabis, you’re probably familiar with the term. Within a few minutes of smoking a bowl, many users experience a sudden increase in appetite. This is frequently accompanied by a heightened appreciation for flavors, which can make moderation a challenge – if you enjoy a bowl of ice cream while sober, you might find out that while high, you really like an entire bucket of the stuff. 

For some cannabis users, the munchies are an unwelcome side effect that makes weight management difficult. Meanwhile, for individuals who have a severe lack of appetite due to cancer treatment, HIV, or an autoimmune disease like ulcerative colitis, the munchies can dramatically improve quality of life. But, enough about that. We already know what the munchies are – but what causes them?

The Science

Well, for starters, we know that THC is primarily responsible for the munchies. As far as we know, CBD isn’t part of this equation. Other cannabinoids have not been studied as extensively as THC and CBD, so we don’t know for sure whether or not they contribute to the munchies. However, considering that they are much less prevalent than THC, it’s safe to say that the munchies are caused by THC, via several different mechanisms:

  • By enhancing your sense of smell. A 2014 study published in Nature Neuroscience used mice as subjects, and found that THC can fit into receptors found in the brain’s olfactory bulb. This heightened the subjects’ sense of smell. This result suggests that part of the reason cannabis users eat more while high is simply the fact that due to a better sense of smell, food becomes more appealing. Interestingly, the researchers also genetically engineered mice that did not have certain cannabinoid receptors in their olfactory bulbs. These mice did not exhibit an increase in appetite after being given THC, which shows that the munchies are very tightly tied to the drug’s effect on the olfactory lobe. The study also found that when mice were intentionally starved for 24 hours, they had increased levels of endocannabinoids in that part of the brain – so, perhaps THC increases hunger by simulating feelings of starvation.
  • By increasing the release of dopamine. THC causes the brain to produce more dopamine, a neurotransmitter that induces feelings of pleasure and helps regulate the brain’s reward system. Some amount of dopamine is normally released when we eat. When we’re high, the brain releases even more, which chemically encourages us to eat more.
  • By increasing the release of ghrelin, a hormone that stimulates hunger. THC activates receptors in the hypothalamus, causing them to produce and release ghrelin.
  • By altering the effects of pro-opiomelanocortin (POMC). POMCs are a set of neurons in the hypothalamus that secrete a chemical called alpha-MSH, which scientists believe send signals to let you know that you’re full (and that you should probably stop eating). Tomas Horvath, a neurobiology professor at Yale, conducted a study to find out how cannabinoids affect this function. He expected THC to “turn off” the POMCs. With the POMCs unable to send the “you’re full” message, cannabis users would just keep eating. This would have explained where the munchies come from… but in fact, something very different happens. Instead of simply turning off the POMCs, THC actually changes their function. Instead of producing alpha-MSH, POMCs start producing beta-endorphins, which actually increase appetite.

The Rimonabant Story

THC manipulates the body’s neurotransmitters to stimulate hunger, but we can also inhibit those receptors to accomplish the reverse. However, it can’t be done without consequences. In 2006, a weight loss drug called Rimonabant was approved for sale in Europe. It worked by blocking the body’s CB1 receptors, which successfully reduced users’ food cravings. However, the endocannabinoid system (ECS) plays an important role in many of the body’s functions, not just hunger. For example, it is also involved in controlling our moods and allowing us to experience happiness and pleasure.

As a result, Rimonabant users didn’t just experience a diminished ability to feel hungry; they also experienced an inability to feel happiness. Rimonabant was taken off the market when users became depressed, and some even committed suicide. This series of events serves to highlight the complexity and the importance of the endocannabinoid system, as well as a need for a greater scientific understanding of both the ECS and of cannabinoids.

With the munchies being such a common effect of cannabis, you might wonder why the average stoner isn’t horribly overweight. Horvath’s study may have an answer. Even while the POMCs are busy producing beta-endorphins and releasing them, they continue to produce and store alpha-MSH. When the THC works its way out of your system, the POMCs release the alpha-MSH, which then induces a reduction in appetite. So, overall, cannabis users probably eat an average amount of food – just on an erratic schedule.

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