Ryan McLaughlin wanted to know what happened inside a rat’s brain when it got stoned. More specifically, whether a well-fed, contented rat — one that had eaten its fill and had absolutely no biological reason to seek more food — would still pull a lever for snacks after inhaling cannabis vapour. The answer was unambiguous. “The sober animals are kind of like, ‘I’m full. Why do I care?’ They don’t put in any effort at all,” says McLaughlin, a professor at Washington State University’s College of Veterinary Medicine. “But you get them stoned again, and even though they’re now full and they’ve eaten, they go right back as if they’re starving.”
That observation, mundane to anyone who has ever raided a kitchen at midnight, turns out to be scientifically consequential. A new study published in the Proceedings of the National Academy of Sciences (PNAS) is among the most rigorous examinations of “the munchies” ever conducted, running parallel experiments in both humans and rodents to pin down not just whether cannabis increases appetite but precisely where in the body this effect originates.
Parallel Experiments: From Pullman to Calgary
The human portion of the study enrolled 82 volunteers aged 21 to 62 from the greater Pullman, Washington community and randomly assigned them to vape either 20 or 40 milligrams of cannabis, or an inert placebo. To ensure the study reflected real-world use, researchers used a “whole-plant” vapor approach rather than synthetic THC injections. This “translational” method allows scientists to see how the complex chemistry of the plant—not just a single molecule—interacts with human behavior.
Then came the snack table. The results were striking in their consistency: regardless of BMI, when the participants had last eaten, their sex, or how much cannabis they’d consumed, those who actually got high ate significantly more food. All of it. Within the first half-hour of snack access, the effect was already pronounced. One finding in particular puzzled Carrie Cuttler, who directs the Health and Cognition Lab at WSU and helped lead the research. “Beef jerky was one of the No. 1 things intoxicated people gravitated toward, which I don’t understand. Honestly, I would have thought chocolate, chips, Rice Krispies treats — things like that.”
Water was also a top choice, likely a physiological response to xerostomia (cottonmouth), caused by THC binding to receptors in the salivary glands.
The rat experiments at the University of Calgary, led by Matthew Hill and Catherine Hume, mirrored these findings with precision. The animals were given operant chambers — essentially boxes where pulling a lever dispensed food — and offered various options after cannabis vapour exposure. Satiated rats who wouldn’t normally bother suddenly worked energetically for food. “The same thing we saw in the humans we saw in the rats,” Hill says. “We kind of thought it would make them want to eat carb-rich foods, but that didn’t seem to be the case. It just seemed to be any food.”
The Mechanism: A Top-Down Brain Hijack
This matters because it starts to tell us something about the mechanism. Previous theories had suggested cannabis might selectively amplify the appeal of sweet or fatty foods — enhancing the hedonic draw of particularly pleasurable options. What the study found instead was something more wholesale: cannabis appears to override the brain’s satiety signals entirely, boosting motivation to eat and reducing what researchers call “food reward devaluation.”
What is Food Reward Devaluation?
Normally, as you eat, the pleasure derived from food decreases—a biological “stop” sign. This study proved that THC keeps the reward value high, meaning the tenth bite of food feels as rewarding as the first, regardless of how full the stomach is.
The body produces its own cannabinoids naturally, molecules that bind to the same receptors as THC and help regulate everything from mood to pain to appetite. In the hypothalamus, this endocannabinoid system is partly responsible for hunger signalling. “But THC hijacks that entire system,” says McLaughlin. “So even though you’re not necessarily hungry, THC can stimulate cannabinoid receptors in the brain and make you feel hungry.”
To confirm that the action is happening in the brain rather than the gut, the Calgary team ran a pharmacological experiment: they blocked cannabinoid receptors in the peripheral nervous system of rats — the network running through the digestive organs — and found this did nothing to reduce cannabis-induced eating. Blocking those same receptors in the brain, though, stopped the effect entirely. Circulating appetite hormones like ghrelin and leptin showed no significant changes, which further rules out a gut-based explanation.
Clinical Implications for Wasting Syndrome
The clinical motivation for this research is profound. Around 4% of the world’s population uses cannabis, yet the physiological basis for its effects has been surprisingly under-studied. For patients suffering from Cachexia (Wasting Syndrome) associated with HIV, AIDS, or chemotherapy, this research provides a scientific roadmap for treatment.
By identifying that “the munchies” are a central nervous system event rather than a digestive one, scientists can move toward identifying specific receptor subtypes. The goal is to produce the appetite-stimulating benefits of cannabis—the “biological override” that saves lives in clinical settings—without the psychoactive “high.”
Further Reading and Resources
The next step is identifying the specific brain circuits involved. Whether such a drug would cause anyone to reach specifically for beef jerky remains, as yet, undetermined.
Study link: https://www.pnas.org/doi/10.1073/pnas.2518863122
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