Recent studies have shown evidence that intense hunger after cannabis use is a neural response that increases the desire to eat, regardless of the body’s actual caloric needs. These findings suggest that cannabis may serve as a medical tool to stimulate appetite in people experiencing weight loss due to chronic illness. This research Proceedings of the National Academy of Sciences.
Cannabis is a plant that contains psychoactive compounds, specifically tetrahydrocannabinol (THC). When a person inhales or ingests cannabis, THC interacts with the body’s endocannabinoid system, a complex network of receptors that helps regulate mood, memory, pain, and appetite. Although intense cravings after cannabis use are frequently mentioned in popular culture, the exact biological and behavioral mechanisms behind this phenomenon are surprisingly understudied.
“Although it seems widely accepted in popular culture that cannabis consumption increases food intake, also known as ‘munch,’ there is a surprising lack of empirical research examining the parameters of munch after inhaling cannabis vapor. In this study, we investigated how vaporization of THC-rich cannabis extract affects food consumption patterns in a controlled environment in both humans and rodents,” said study author Matthew N. Hill, a professor at American University. Lives in Calgary and is Director of the Matheson Center for Mental Health Research and Education.
Scientists conducted research to fill gaps in the scientific literature. They wanted to understand exactly how inhaled cannabis changes dietary patterns, macronutrient preferences, and the brain’s reward system. Determining whether this feeling of hunger originates from the brain or the gut could help with treatments for anorexia.
To investigate these questions, the scientists designed two parallel experiments involving both human participants and laboratory rats. The human clinical trial involved 82 volunteers between the ages of 21 and 62 from the Greater Pullman, Washington, area. The researchers randomly assigned these participants to one of three groups in a highly controlled environment.
Participants inhaled vapor containing either 20 milligrams of cannabis, 40 milligrams of cannabis, or a placebo plant material. The placebo material contained no psychoactive compounds, and neither the participants nor the scientists knew what dose was being administered. After completing the approximately 1-hour cognitive memory test, volunteers were given access to a variety of snacks and beverages.
The scientists measured the participants’ food intake over time and asked them to rate the taste of the items. This human study provides evidence that inhaling cannabis sharply increases food consumption. During the first 30 minutes after ingesting food, participants who received either dose of cannabis ingested significantly more carbohydrates, fat, and protein than the placebo group.
The data shows that cannabis did not change the specific types of foods participants preferred. Instead, the volunteers simply ingested larger amounts of all available macronutrients without proportionally changing their diets. The researchers also found that the amount of time since participants last ate had no effect on the amount of food they consumed after using cannabis.
Fasting had no effect on the amount of snacks eaten during the study. So it wasn’t caused by hunger. Additionally, cannabis had no effect on participants’ ratings of the tastes provided. This suggests that this plant does not necessarily make food taste better, but rather causes a general, non-specific urge to burn calories.
In a parallel animal study, researchers exposed adult male and female rats to cannabis vapor or a neutral control vapor. The scientists then closely observed the rodents’ feeding behavior. Similar to human volunteers, rats exposed to cannabis vapor consistently ate more food than the control group.
This increase in calorie consumption occurred regardless of the sex of the rats. To test whether cannabis could override satiety, scientists fed a group of rats a highly appealing meal until they were completely satisfied. After being exposed to cannabis vapor, these satiated rats began eating again as if they were starving.
When given a choice between high-fat and high-carbohydrate foods, rats exposed to cannabis ate more of everything. This action effectively abolished their existing food preferences. The scientists then designed a task to measure the animals’ motivation to obtain food.
Rats were trained to press a lever to receive a sweet treat. As the experiment progressed, the number of lever presses required to obtain a single treat steadily increased. Rats under the influence of cannabis consistently worked harder and pressed the lever more times than non-drinking rats.
This highly motivated behavior persisted even when the researchers reduced the appeal of the sweet treats. The scientists achieved this reduction in value by pre-feeding the rats or by combining the food with a substance that causes mild nausea. The results suggest that cannabis increases the brain’s reward assessment of food, increasing the animal’s desire to eat even in the absence of a biological need.
To understand the physical mechanisms behind this intense hunger, the researchers measured the blood levels of various appetite-regulating hormones in rats. They tested hormones such as ghrelin, leptin, and insulin, which typically signal hunger and satiety in the body. They found that cannabis exposure did not change the levels of these metabolic hormones.
This lack of hormonal changes provides evidence that the urge to eat does not originate from the digestive system. The scientists then used specific drugs to block cannabinoid receptors in different parts of the rats’ bodies. Blocking receptors in the peripheral nervous system, including in the intestines and other organs, did not stop cannabis bingeing.
But the results changed when scientists blocked cannabinoid receptors located directly in the brain. Because the receptors in the central nervous system were blocked, the rats no longer showed an increase in appetite after exposure to cannabis. This suggests that cannabis hijacks the brain’s natural appetite-regulating center, triggering a strong drive to seek food.
“Our data confirms a widely held belief and robustly found that vaporizing cannabis actually increased food intake,” Hill told SciPost. “Interestingly, this food intake was relatively short-term, not specific for any macronutrient (both human and rodent subjects intoxicated with cannabis vapor increased their intake of fat, carbohydrates, and protein indiscriminately), and was sensitive to taste. A more detailed study in rodents found that the munchies were actually due to cannabis making food more rewarding and motivating them to eat it.
“Munchies are real, and cannabis can really make food more rewarding and more motivating to eat food. Many people think this is just a fun side effect of cannabis, but this ability to stimulate food intake and make food more rewarding can actually be harnessed therapeutically to help people who suffer from wasting-related disorders or who have developed strong aversions to food due to interventions such as nausea-inducing chemotherapy.”
Although this study provides extensive research on cannabis-induced hunger, there may be some misconceptions and limitations to consider. This study primarily focused on the immediate and short-term effects of inhaling cannabis. No evidence is provided about how regular, long-term cannabis use affects daily caloric intake or overall body weight over time.
“The munchies caused by marijuana don’t actually mean that marijuana users will develop obesity or metabolic problems,” Hill said. “Our study suggests that the effects of cannabis on food intake are relatively temporary and do not last long. Additionally, several large studies have consistently found that obesity rates are lower in cannabis users than in the general population.”
The human participants were also experienced cannabis users, so results may be different in people who have never used cannabis. Future research should investigate how different formulations of cannabis affect appetite. The study used a specific type of cannabis that is high in THC, but other compounds in the plant may cause different behavioral responses.
Scientists also hope to map the exact neural circuits in the brain that respond to inhaling cannabis. Understanding these specific pathways tends to be an important step in developing targeted medicines. These future discoveries could ultimately help patients suffering from severe anorexia due to chronic illness.
The study, “Cannabis induces acute hyperphagia in humans and rodents through increased reward valuation of food acquisition and motivation to acquire food,” was authored by Katherine Hume, Carrie Cutler, Samantha L. Baglot, Lucia Jaborshkova, Ryan J. McLaughlin, and Matthew N. Hill.
