Where do the munchies come from?

Posted at 11:28 AM, Feb 18, 2015
and last updated 2015-02-19 17:47:48-05

Most people get a powerful urge to eat after smoking or ingesting marijuana, otherwise known as getting the munchies. The tendency to chow down has been known – and commented upon – for decades.

But where does it come from?

What happens inside the pot-altered brain to induce hunger, even when we’re full - has attracted quite a bit of research lately. Some commercial growers have even started cultivating strains of so-called “skinny pot” that they claim is less likely to bring on the munchies.

The most recent science finding, from a new study by Yale School of Medicine scientists published Wednesday in the journal Nature, shows that the urge is driven largely by neurons in the brain that normally work to suppress rather than spur the appetite.

Working with genetically-altered mice, a team led by neurobiologist Tamas Horvath, director of the Yale Program in Cell Signaling and Neurobiology of Metabolism, was able to monitor what goes on in the brain circuitry by selectively manipulating the cellular pathways that control marijuana’s action in the brain.

The same mechanism that normally turns off desire to eat instead becomes a driver to munch in the presence of pot.

“It’s like pressing a car’s brakes and accelerating instead. We were surprised to find that the neurons we thought were responsible for shutting down eating were suddenly being activated and promoting hunger, even when you are full,’’ Horvath said in a press release. “It fools the brain’s central feeding system.”

Understanding pot’s hunger promotion is useful both in understanding how the drug influences the brain, but also could offer new medical benefits, like new pathways to help cancer patients who lose their appetite during treatment. The study was supported in part by the National Institutes of Health.

Our brains have a natural system of receptors that play a role in regulating emotions, memory and pain sensation as well as appetite, which is all subject to disruption when we use cannabis.

In another study published last week in the journal Nature Neuroscience, a team of European researchers also working with mice found that pot’s active ingredient (THC or tetrahydrocannabinol) fires up receptors in the olfactory bulb, sharply increasing the ability to smell and taste food, another likely spur to binging.

Earlier research has shown pot affects the influence of the pleasure signaling chemical dopamine in the brain, and may also impact release of the hunger-stimulating chemical ghrelin.

Horvath and others say it’s still unclear which of these mechanisms might also be linked to bringing about a marijuana high.

[Also by Lee Bowman: Men will donate more if it helps them]

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