Jeff Chen, director of University of California, Los Angeles (UCLA) Cannabis Research Initiative, said the endocannabinoid system can be thought of like a series of keyholes. THC, the main chemical compound in marijuana that causes the sensation of being high, is like a key.

When a person consumes marijuana, the THC ‘turns on the engine of our cells and tells it to do certain things’.

Research suggests that THC interacts with ghrelin, a hormone secreted by the stomach that stimulates appetite. Synthetic THC has even been approved by the Food and Drug Administration (FDA) as a treatment for people with HIV-induced anorexia because of its appetite-enhancing properties.

“We don’t know the threshold for increased appetite, but I suspect it comes down to our bodies and tolerance,” Chen said. “Some folks consume hundreds of milligrams of THC a day and can walk around, and others are bedridden for 24 hours.”

CBD, another well-known cannabinoid, can’t cause the munchies

“It looks like rather than fitting in [the keyhole], CBD might actually attach next to the keyhole and make it more difficult for THC to bind to [the keyhole],” he said. That means consuming CBD could actually limit THC’s side effects.

Chen added that compounds like THC interact with the metabolism. That could have something to do with previous findings that marijuana has little to no effect on body weight, but says more research needs to be done.