Science Behind Munchies: Why Cannabis Causes Hunger

Any cannabis user who has used the substance knows that some strains, especially ones with tetrahydrocannabinol (THC), cause them to raid the refrigerator a few moments later.

But what is this phenomenon that is called the munchies? And how does cannabis cause this in users – medical and recreational alike?

To answer this question, scientists hotboxed lab rats. Scientists from Washington State University wanted to find whether there was a correlation between the gut’s control of food and whether it can impacts mood, motivation, learning, and even addictive behaviors.

“We discovered that when you do weight loss surgery or bypass surgery on people, someone who previously never drank alcohol [may] turn into an alcoholic,” says Jon Davis, a Washington State University assistant professor in integrative physiology and neuroscience.

“It actually clued me into this very powerful communication between the gut and the brain.”
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The endocannabinoid system (ECS) plays a vital role in managing the appetite centre of the brain through the expression of endocannabinoid receptors known as CB1 and CB2. These receptors are expressed all over the central and peripheral nervous systems and regulate processes such as fertility, mood, reward, memory, and appetite.

Davis’ team slowly vaporized the rats with 7.8% THC rather than injecting it intravenously as most experiments do so they would achieve better results. Slow vaporization also ensured the rats would feel the intoxication from the THC in a visible manner.

What they discovered was that cannabis impacted the genes that encoded glutamate, a major type of excitatory neurotransmitter that sparked feeding in the hypothalamus of the brain. When glutamate was increased in an animal, they fed. When it was decreased, as it was after cannabis was given to the rats, appetite was suppressed.

Eventually, however, the rats still went back to feeding. Davis and his research partners found that after exposure to cannabis, grehlin levels began to gradually climb in the rodent. Ghrelin is a hormone found in the stomach that affects appetite stimulation.

“We figure right after the rat consumes marijuana, grehlin can’t really do its thing because the glutamate is turned off,” said Davis. “But when that turns back on, grehlin can work and that’s when you have an appetite again. That’s why there’s a delay.”

Davis’ work in understanding why there is a delay could have potentially groundbreaking results. Obese patients who need their appetites inactivated could see viable treatments with cannabis ahead. Meanwhile, patients suffering from anorexia and cancers can potentially have their appetites activated through this same process using cannabis.

It is important to note that cannabis is used as a treatment for anorexia and cancer currently, but it is not endorsed by either Health Canada or the FDA.

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