Victoria Turk highlights the latest research:
A new study published in Nature Neuroscience offers an answer: THC, marijuana’s active ingredient, acts on certain receptors in the brain related to your sense of smell. It essentially makes you smell food more, which increases your appetite, and leads you to eat more. That’s what seems to happen in fasted mice, at least.
Joseph Stromberg’s takeaway:
THC—and, by consequence, marijuana—does much of its work by manipulating the same pathways that the brain uses to normally regulate the senses. But perhaps most interesting is that the new study hints at a compelling metaphor for the way THC manipulates this natural system:
it mimics sensations felt when we’re deprived of food. As a final test, the researchers forced some mice to fast for 24 hours, and found that this drove up levels of natural cannabinoids in the olfactory lobe. Not surprisingly, these starved mice showed greater scent sensitivity and ate much more too.
Most intriguing, the genetically engineered mice with olfactory lobes that lacked cannabinoid receptors did not show increased scent sensitivity or appetite even when they were starved. This indicates that both THC and the natural cannabinoids that result from starvation are acting on the same neural pathway to allow us to smell and taste with greater sensitivity, and thus eat more. In other words, THC appears to give us the munchies by convincing our brains that we’re starving.
This discovery could have applications in medicine:
If the findings hold true in humans, they could yield novel approaches to treating eating disorders, by manipulating the link between smell and appetite in our brains. New obesity treatments could be possible, by interfering with cannabinoid signaling to reduce people’s hunger drive. (The drug company Sanofi-Aventis introduced just such a cannabinoid-blocking drug for obese patients in 2006, according to New Scientist, but it was withdrawn because it sometimes produced severe anxiety and depression.) Conversely, a drug could enhance cannabinoid signaling for people who suffer from appetite loss, such as cancer patients.