It turns out rats get the munchies too.
New research from the University of Calgary digs into the effects of cannabis on rats, particularly when it comes to appetite.
“We exposed them to cannabis vapour and indeed, were able to very, very reliably see what we could call the munchies,” said University of Calgary neuroscientist Dr. Matthew Hill.
“For the first hour after being exposed to cannabis vapour and getting intoxicated, the rats kind of went to town eating.”
Cannabis activates the brain circuits that are involved in hunger and eating, tricking the brain to want fatty, sugary food.
Hill said most people are familiar with the munchies, and the idea that using cannabis creates an inclination to snack. But he says there was also a common belief that the munchies are more of a placebo effect than a real physiological occurrence.
Because people have been reporting this phenomenon for so long, Hill doubted it was just a placebo effect.
“One of the problems was that most animal work had been using injectable forms of cannabinoids, like injectable forms of THC, and the way that that affects behavior is really quite different than inhalation, which is how the majority of humans consume cannabis,” he said.
“And so, once we had developed and worked with some of our collaborators, this ability to create vapour delivery of cannabis, we did a rat version in our lab.”
Stoned rats eat even when they’re full
The University of Calgary’s joint study with Washington State University offered some interesting insights into the cravings rats get when they’re stoned, particularly when they weren’t hungry before getting high.
“The animals that had the placebo, so they didn’t get any cannabis, they’re full. So then you give them access to food and they do nothing,” Hill said.
“But you get them stoned and they act as if they’re starving again.”
And their favourite foods?
“We thought they were going to really like carbs,” Hill said. “That turned out to not be true.”
“It just seems to be food regardless of the composition. We give them high fat, we give them high carb, whatever. They seem to like everything.”
And when Washington State University researchers conducted a parallel study with high humans, people had a cafeteria-style selection of food to choose from — and one snack seemed to stand out among stoned subjects.
“They seem to love beef jerky,” Hill said. “That was one of the things that got consumed the most.”
What do these findings mean for humans?
Beyond providing evidence to suggest the munchies are actually real, the study has significant implications for people struggling with certain conditions, says Hill.
“One of the few recognized medical uses of cannabis is actually in the context of chemotherapy-induced nausea,” he said.
“The nausea associated with chemotherapy can create a malaise that causes what we call the condition ‘taste aversion’ against foods that are eaten in that time around it,” he said.
“You can kind of think of this like if you’ve been sick or someone’s had a hangover, and they’re really nauseous, and if you try and eat food during that period, your brain pairs that food with the nausea and makes you not want to eat it anymore.”
Hill says there’s evidence that cannabis can suppress nausea, acting slightly better than some standard drugs.
And in the aftermath of chemotherapy, once the initial wave of nausea has passed, cannabinoids can stimulate the desire to eat, he said.
There could also be implications for helping people with eating disorders like anorexia, Hill said.
“There is some thoughts that perhaps using cannabinoids in very, very specific manners may be able to wait to reduce some of the anxiety associated there, but also kind of enhance food reward to try and drive feeding behavior a little bit more,” he said.
He said that remains “highly speculative,” however.
Why rat results matter
The University of Calgary’s Dr. Keith Sharkey, who has closely studied digestion and nausea, says the study provides valuable insight into the science of the munchies.
“The fact that it’s found in mammals, not just humans, is illustrative of the fundamental importance that the cannabinoid system has in regulating bodily actions, including food intake and more generally in energy balance,” he said.
“It’s not a surprise, but it’s a great piece of work that they did to demonstrate that.”
Alberta’s rat control program has been in place for 75 years. The program, established in 1950, has workers patrol the border between Saskatchewan and Alberta year-round.
Sharkey said researchers can’t assume all mammals get the munchies simply because humans do, and that studies like this are needed to prove that.
“Humans have a lot of different behaviors that animals don’t have, but when one sees it fundamentally across different species, it illustrates the physiologic significance of it,” he said.
But registered dietician Grace Beda says that while the study is promising, it shouldn’t be interpreted as evidence that cannabis is the best medical option for patients.
“A lot of cancer patients who are struggling with appetite come to us and ask about cannabis usage, and we don’t routinely recommend it on an official basis because the research is so mixed,” she said.
Beda said clinical research has not shown cannabis use guarantees significant or meaningful weight gain.
She said that while inhaled THC has been shown to be more effective for appetite stimulation than oral drops or edibles — which is in line with the study’s findings — clinicians do not recommend smoking or vaping for cancer patients undergoing treatment.
“You don’t want to be taking in foreign substances into your lungs,” Beda said.
“So that’s why we always say, ‘okay, if you want to try it, you can try the drops or the oils or whatever other non-inhaled forms,’ and that’s sort of where the efficacy goes down or is quite mixed.”
The human portion of the study involved 82 study participants between the ages of 21 and 62 inhaling vaporized cannabis.
