If you’re like most people, you simply can’t pass up the opportunity to partake in a piece of chocolate (or five). Some have even said that chocolate melting on the tongue is better than a kiss. But why do we love chocolate so much?

Our cravings can be traced to two places: Our guts—studies have shown that chocolate lovers have different bacteria in their intestines than non-chocolate lovers—and our brains. We crave chocolate because eating it results in the production of opioids, which dull pain and increase levels of dopamine, a neurotransmitter in the brain’s reward system that helps us experience pleasure. (Drugs like cocaine and amphetamines work directly on the dopamine system.)

Chocolate can have many health benefits in moderation, but often, people can’t stop popping truffles—and scientists might know why. In a recent study, researchers working with rats injected a drug directly into the neostriatum, a region of the brain primarily associated with movement. When the rats began to eat M&Ms, a naturally occurring chemical produced in that region of the brain, called enkephalin, surged, increasing the rats’ desire to eat the candies. The animals ate twice the number of M&Ms they would have eaten normally.

Alexandra DiFeliceantonio, a researcher at the Universty of Michigan, Ann Arbor who ran the study, says this same area is active when obese people see food, or when drug users take in a drug scene. “This means that the brain has more extensive systems to make individuals want to overconsume rewards than previously thought,” she said. "It seems likely that our enkephalin findings in rats mean that this neurotransmitter may drive some forms of overconsumption and addiction in people."