Scientists have zoomed in on why cannabis makes people hungry -- the so-called "munchies". Aside from solving a long-standing curiosity, this could lead to treatments for appetite loss in chronic illness, researchers say.
As anyone who's ever had a taste of the Devil's grass (a.k.a. cannabis) can attest, one of the after-effects is a sudden and strong desire for food -- especially sweets. However, while this effect has been observed for decades, its cause and mechanism were not known. But with the surge of cannabis legalization measures (both for recreational and medical purposes), understanding the "munchies effect" became even more important.
"We all know cannabis use affects appetite, but until recently we've actually understood very little about how or why," explained Jon Davis, Ph.D., researcher in the Department of Integrative Physiology and Neurosciences at Washington State. "By studying exposure to cannabis plant matter, the most widely consumed form, we're finding genetic and physiological events in the body that allow cannabis to turn eating behavior on or off."
Scientists already knew that the psychological effects of cannabis (the "high") are caused by a family of compounds called cannabinoids, particularly delta-9 tetrahydrocannabinol (THC). But the ability of THC to stimulate appetite is much less understood.
The Hunger Hormone
Davis and colleagues designed a study on rats, with a vapor exposure system to mimic how people often consume cannabis. This way, they were able to control the dosage, which was closely monitored throughout the study. First, researchers observed that even a brief exposure to cannabis prompted rats to eat a meal -- even right after they'd eaten.
"We found that cannabis exposure caused more frequent, small meals," stated Davis. "But there's a delay before it takes effect."
Then, the team observed a surge in a hormone called ghrelin. Ghrelin, often called the "hunger hormone," regulates appetite and plays a significant role in the distribution and rate of use of energy. When the stomach is empty, ghrelin is secreted as a message to the brain that it's time to look for food. It seems that cannabis stimulates ghrelin secretion, which in turn makes us hungry.
In order to confirm that this was the cause of the increased appetite, researchers then administered a second drug which inhibits ghrelin production -- and cannabis no longer stimulated eating.
Of course, there are a few distinctions to be made here. For starters, it's a rat study, and there's no guarantee that the same effect is carried out similarly on humans -- although Davis is cautiously confident that this will be the case. Secondly, there is a myriad of different cannabis strains out there, each with its own THC concentration and individual characteristics. In this study, researchers only used marijuana grown at the University of Mississippi, which has an extremely low THC concentration (about 7.8%). Commercial marijuana often reaches THC concentrations over 20%. This makes it harder to assess if the effect is uniform across all strains, or how it may relate to other properties like THC content.
However, this is yet another compelling argument in the case for the medicinal use of cannabis. While some of the drug's purported benefits have certainly been overstated, there is still a case to be made for some medical properties of marijuana -- in this case, Davis says, as a way to promote appetite. Patients undergoing taxing clinical treatments often find it hard to maintain a healthy appetite.
“Something that we want to pursue in my lab is seeing whether the effect of THC concentrations could cause different results — meaning, maybe they would eat a little sooner or delay feeding a little longer,” Davis told Inverse. “Having said that, I’m absolutely confident that when people are going to inhale or vaporize marijuana, they are going to have an increase in appetite.”
The results are currently under review.
Scientific Reference: Investigating the Neuroendocrine and Behavioral Controls of Cannabis-Induced Feeding Behavior. JF Davis, PQ Choi, J Kunze, P Wahl, Washington State University Pullman. Presented July 2018, Society for the Study of Ingestive Behavior, Bonita Springs, FL.