You’re minding your own business when it hits you: the overwhelming desire for a juicy burger. Where did that sudden meat-need come from? Scientists at Johns Hopkins University may have an answer: a circuit inside your brain that seems to cause protein cravings. The researchers published their findings in the journal Science.

Animals like us need nutrients like protein in order to keep going. Many scientists believe that food cravings are our bodies’ way of motivating us to seek those nutrients out. Yet the exact neurological source of these craving impulses has been something of a mystery.

The authors of the current study started very, very small, looking at cells and circuits in the brains of fruit flies. Activities like mating can increase a fly’s protein cravings, so the researchers decided to focus on female flies that had recently had sex. The scientists monitored the flies' little brains while withholding the bugs’ favorite protein-rich meal of yeast. As the flies’ protein hunger increased, the researchers saw a small circuit of neurons they dubbed DA-WED light up.

To double-check that these cells were in fact craving-related, the scientists shut them down, then offered the recently mated females access to as much yeast as they wanted. But while the circuits were off, the yeast just didn’t seem all that appealing.

Shutting down the DA-WED cells didn’t make the flies drink any less water, nor did it make them eat less in general. They just didn’t feel like getting their yeast on.

These are early findings yet. More research will be needed to confirm the craving/brain cell link in flies, and we’ll definitely need more experiments before we can say the same is true in people. And the average burger also contains two other addictive substances: fat and refined carbohydrates (in the bun).

Still, this paper is an interesting start.

“Further characterization of these and related circuit mechanisms should help delineate the fundamental principles governing protein-specific hunger,” the authors say. “A better understanding of how animals choose to consume protein may also have implications for the treatment of obesity.”