A pedestrians walks past the Little Green Pharmacy medical cannabis dispensary in Denver, Colorado, on Tuesday, August 2, 2011. Photo by Randall Benton/Sacramento Bee via Getty Images

Potheads and doctors have known for a long time that smoking weed increases appetite, said Tamas Horvath, a neurobiologist at Yale University School of Medicine. But how does a drug make people ravenously hungry?

“What drives that, nobody has ever really known. We accidentally bumped into that,” Horvath told The Washington Post.

In a paper published in the journal Nature Neuroscience this week, Horvath and his colleagues found that cannabis tricks your brain into thinking you’re starving, even if you’re full.

“It’s like pressing a car’s brakes and accelerating instead,” Horvath said in a press release. “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. It fools the brain’s central feeding system.”

Our brains produce their own cannabinoids, lipids that help control our appetite, mood, memory and pain reception. Tetrahydrocannabinol, or THC, produced in marijuana latches on to cannabinoid receptors in our brain, mimicking the same chemicals.

Horvath found that THC flips a switch in the mouse’s hypothalamus. Instead of producing the chemical that signals you’re full, suddenly neurons start telling the hypothalamus you’re hungry.

“Even if you just had dinner and you smoke the pot, all of a sudden these neurons that told you to stop eating become the drivers of hunger,” Horvath told NPR.

Horvath’s lab found in earlier studies that cannabis also plays with cannabinoid receptors in olfactory bulb, which not only makes food smell and taste more intense, it also affects how much we eat.

Mice make a good model, but further research is needed to determine if this is what is happening in humans too, Horvath said.

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