Everybody knows it: Weed makes you hungry. Smoking a bowl sends you searching for snacks. Hitting a spliff leaves you craving all kinds of sweets. Ripping a bong gives you the munchies. We don't know why. Science is getting close though, especially after this week.
There's a growing pile of research into weed and our brains, and particularly this curious side effect. Yale Medical School recently published one of the more definitive studies on the neurological effects of marijuana on hunger. It's an important step forward for a few different reasons. For one, hunger-inducing medications can save the lives of cancer patients and others with problems eating. Pharmaceutical companies are also intensely interested in figuring out the exact mechanism for munchies in order to make a better weight loss pill. The idea there is that if we know how to turn on hunger, we can figure out how to turn it off.
This is what science has got so far.
Tricking the Brain
The Yale study just gave us a much better idea of exactly how cannabinoids, namely THC, interact with neurons. In other words, the researchers figured out exactly how smoking weed affects the part of your brain that controls hunger. This is not the only process that causes the munchies, but it's arguably the most important one.
It all comes down to a cannabinoid receptor called CB1R and how it stimulates a cluster of nerve cells called pro-opiomelanocortin (POMC) neurons. The POMC neurons are located in the hypothalmus, one of the most primitive part of the brain that's controls instincts like sexual arousal and hunger. The fact that weed would affect these neurons is not a huge surprise. It's long been known that the CB1 receptor was linked to the hunger side effect. However, POMC neurons are normally responsible for telling you when you're full, not making you hungry.
So why would stimulating the part of the brain that tells you to stop eating make you want to eat more? Past experiments have shown that deactivating the POMC neurons in mice will cause them to eat nonstop and get super fat. However, in a similar experiment on mice, the Yale scientists pretty much saw the exact opposite happen. When given cannabinoids, the POMC neurons shifted into high gear, and they also activated a receptor in the neurons that caused them to make a U-turn. Instead of sending signals that they were full, the neurons produced endorphins that stimulated the appetites of the mice. It gave them the munchies.
If you've ever been blazed at a music festival, you'll know that weed also makes you want food in a way that transcends traditional hunger. Know why? It's the olfactory appeal.
Again, it's the CB1 receptors doing work. Almost exactly one year ago, a pan-European group of scientists published a study about marijuana's effect on the senses, namely the olfactory bulb. In no uncertain terms, they found that the CB1 receptor stimulated a different set of neurons that led to "increased odour detection" in mice.
That's a real geeky way of saying that pot heightened the little rodents' sense of smell. The experiment also showed that increased odour detection was linked to increased appetite, aka the munchies.
There is probably more going on here, too. The CB1 receptors are part of the endocannabinoid system which is involved in a whole host of things—from mood to memory, hunger to pain. So while cannabinoids are jacking up your sense of smell, they're also tweaking physiological processes related to anxiety, metabolism, muscles, and sex.
These facts are at the root of the huge push to fund more research into marijuana's medicinal promise. If smoking the plant can work miracles with cerebral palsy patients, imagine what we could do if we isolated the specific effects of cannabinoids.
All that said, getting high is pretty fun. In the right circumstance, the munchies are super fun. This is because marijuana actually makes food taste better.
There's a study that supports this claim as well, believe it or not, and the CB1 receptor is responsible for the taste-enhancing effect. The cannabinoids actually stimulate your brain's dopamine factories. Good food already boosts dopamine levels, and if you're high, that deliciousness boosts those dopamine levels even more. In other words, that pizza that arrived while you were smoking a joint in your mum's basement tastes like the best pizza you've ever had, because your brain actually thinks it's the best pizza you've ever had.
That's not to say that the munchies are always amazing. It doesn't help that smoking a bowl makes you feel tired and lazy, so you're consuming tons of calories and then just sitting there watching Guardians of the Galaxy on loop wondering why you didn't read more comic books as a kid.
This is to say that marijuana's effects on the brain can be very positive. As outdated and often draconian laws banning cannabis are lifted across the US, more and more researchers are getting the opportunity to study the plant and find more medical applications for it. They've even figured out how to make a compound that keeps marijuana from getting you high. Not that we endorse that. No way.