Scientists uncover the neurological mechanisms behind cannabis-induced “munchies”

A recent study provides evidence that the intense hunger following cannabis use is a neurological response that increases the motivation to eat, regardless of a body’s actual need for calories. These findings suggest that cannabis could serve as a medical tool to stimulate appetite in individuals experiencing weight loss from chronic illnesses. The research was published in the Proceedings of the National Academy of Sciences.

Cannabis is a plant that contains psychoactive compounds, most notably tetrahydrocannabinol, or 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. While pop culture frequently references the intense food cravings that follow cannabis use, the exact biological and behavioral mechanics of this phenomenon remain surprisingly understudied.

“While in pop culture it seems widely accepted that consumption of cannabis increases food intake, also known as ‘the munchies,’ there is a surprising lack of empirical research that has examined the parameters of the munchies following inhalation of cannabis vapor. This study used both human and rodent subjects to examine how vaporization of THC enriched cannabis extracts could influence food consumption patterns in a controlled setting,” said study author Matthew N. Hill, a professor at the University of Calgary and director of the Mathison Centre for Mental Health Research and Education.

The scientists conducted the research to fill the gap in the scientific literature. They wanted to understand exactly how inhaled cannabis alters eating patterns, macronutrient preferences, and the brain’s reward system. Determining whether this hunger stems from the brain or the gut could help inform treatments for appetite loss.

To investigate these questions, the scientists designed two parallel experiments involving both human participants and laboratory rats. The human clinical trial included 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 setting.

Participants inhaled vapor containing either 20 milligrams of cannabis, 40 milligrams of cannabis, or a placebo plant material. The placebo material lacked psychoactive compounds, and neither the participants nor the scientists knew which dose was administered. After completing about an hour of cognitive memory tests, the 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. The human study provides evidence that inhaled cannabis acutely increases the consumption of food. In the first 30 minutes of food access, participants who received either dose of cannabis ate significantly more carbohydrates, fats, and proteins than those in the placebo group.

The data indicates that cannabis did not alter the specific types of food the participants preferred. Instead, the volunteers simply ate a larger quantity of all available macronutrients without changing their proportional diet. The researchers also found that the duration of time since a participant last ate did not influence the amount of food they consumed after using cannabis.

Fasting had no impact on the volume of snacks eaten during the trial, meaning the hunger was not driven by an empty stomach. Additionally, the cannabis did not affect the taste ratings provided by the participants. This suggests that the plant does not necessarily make food taste better, but rather drives a general, non-specific urge to consume calories.

In the parallel animal study, researchers exposed adult male and female rats to either a cannabis vapor or a neutral control vapor. The scientists then closely observed the feeding behaviors of the rodents. Much like the human volunteers, the rats exposed to cannabis vapor consistently ate more food than the control group.

This increase in calorie consumption occurred regardless of the rats’ sex. To test if cannabis could override feelings of fullness, the scientists allowed a group of rats to eat a highly appealing meal until they were completely satisfied. After exposure to cannabis vapor, these full rats began eating again as if they were starving.

When given a choice between high-fat and high-carbohydrate foods, the cannabis-exposed rats ate more of everything. This behavior effectively abolished their pre-existing food preferences. The scientists then designed a task to measure the animals’ motivation to obtain a food reward.

The rats were trained to press a lever to receive a sugary treat. As the experiment progressed, the number of lever presses required to get a single treat steadily increased. Rats under the influence of cannabis consistently worked harder and pressed the lever more times than the sober rats.

This highly motivated behavior persisted even when the researchers made the sugary treats less appealing. The scientists achieved this devaluation by either feeding the rats beforehand or pairing the food with a mild nausea-inducing substance. The results suggest that cannabis increases the brain’s reward valuation for food, making the animals highly motivated to eat even when they have no biological need.

To understand the physical mechanics behind this intense hunger, the researchers measured the rats’ blood levels for various appetite-regulating hormones. They tested for hormones like ghrelin, leptin, and insulin, which typically signal hunger or fullness in the body. They found that cannabis exposure did not alter the levels of any of these metabolic hormones.

This lack of hormonal change provides evidence that the urge to eat does not originate in the digestive system. Next, the scientists used specific medications to block cannabinoid receptors in different parts of the rats’ bodies. Blocking the receptors located in the peripheral nervous system, which includes the gut and other organs, did not stop the cannabis-induced overeating.

However, the results changed when the scientists blocked the cannabinoid receptors located directly in the brain. With their central nervous system receptors blocked, the rats no longer exhibited an increased appetite after cannabis exposure. This suggests that cannabis hijacks the brain’s natural appetite-regulating centers to trigger a strong motivation to seek out food.

“Our data confirmed the widely held beliefs and reliably found that cannabis vaporization did indeed increase food intake,” Hill told PsyPost. “Interestingly, this food intake was relatively short lived, was not specific to any macronutrient (both human and rodent subjects intoxicated on cannabis vapor indiscriminately increased consumption of fat, carbs and protein) and was not directly related to increased sensitivity to flavor. More detailed studies in rodents identified that the munchies was actually due to cannabis enhancing the rewarding aspects of food and increased motivation to eat food.”

“The munchies are a real thing and cannabis can genuinely increase the rewarding value of food and increase your motivation to eat food. While many people think this is just funny side effect of cannabis, this ability to stimulate food intake and make food more rewarding can actually be leveraged therapeutically to help people suffering from wasting related disorders or who have developed intense aversions to food through interventions like chemotherapy which produce nausea.”

While this research provides an extensive look at cannabis-induced hunger, there are some potential misinterpretations and limitations to consider. The study primarily focused on the immediate, short-term effects of cannabis inhalation. It does not provide evidence on how regular, long-term cannabis use might impact daily calorie intake or overall body weight over time.

“Cannabis induced munchies do not actually mean that people who use cannabis will develop obesity or metabolic issues,” Hill said. “Our work suggests that the effects of cannabis on food intake are relatively transient and not long lasting. More so, there are several large scale studies which have consistently found that cannabis users have lower rates of obesity then the general population.”

The human participants were also experienced cannabis users, which means the results might differ in people who have never used the plant. Future research should investigate how different formulations of cannabis might affect appetite. The current study used a specific type of cannabis that was high in THC, but other compounds in the plant might yield different behavioral responses.

Scientists also hope to map the exact neural circuits in the brain that respond to cannabis inhalation. Understanding these specific pathways tends to be an important step in developing targeted medical therapies. These future discoveries could eventually help patients suffering from severe appetite loss due to chronic diseases.

The study, “Cannabis produces acute hyperphagia in humans and rodents via increased reward valuation for, and motivation to, acquire food,” was authored by Catherine Hume, Carrie Cuttler, Samantha L. Baglot, Lucia Javorcikova, Ryan J. McLaughlin, and Matthew N. Hill.