Feeling cranky when we wait too long to eat is such a common feeling, there’s even a term for it: “hangry,” a portmanteau of “hungry” and “angry.” But even if it’s a well-observed phenomenon, most of us are unfamiliar with the science behind it. 

It turns out feeling “hangry” doesn’t mean you’re a short-tempered or impatient person—even the most seemingly laid-back people can experience hunger-based anger. According to Brenda Bustillos, a dietician at Texas A&M Health Science Center School of Public Health, “What’s interesting about hanger is it’s actually a survival mechanism.” 

Hanger, Bustillos explains, is our brain’s way of telling us we’re low on glucose, and we need to refuel: “The amount of glucose available for the brain declines as more time passes between meals.” Bustillos says. “Food is important because when glucose levels become too low, our brain triggers the release of stress hormones.” 

On the one hand, hangry feelings send us an important signal: It’s time to eat. On the other, part of the reason we experience hanger—rather than simple hunger, which also tells us it’s time to chow down—is because it’s harder for us to control our emotions when our brains are low on glucose. Bustillos notes, “In a brain lacking glucose, it’s harder to control signs of anger. Acute bouts of hunger trigger the release of stress hormones which makes it harder to manage our anger and irritability.” 

Ultimately, our hanger may be for the best. “If you’re an animal and you’re hungry, you need food to survive,” Paul Currie, a professor of psychology at Reed College told Time. “So it’s natural that you would feel anxious and irritable and preoccupied until you’ve met that need.”

But, for many of us, differentiating hunger-related anger from other forms of anxiety or frustration can be surprisingly difficult. In one 2014 study, Ohio State University researchers found that spouses were significantly more likely to fight with each other in the evenings if their blood sugar was low. And, according to The Huffington Post, some scientists are even studying whether low glucose levels may be a risk factor for violent behavior. 

Fortunately, there’s a simple cure for hanger: just grab a bite to eat. And, if you’re experiencing frequent hanger despite regular meals, Bustillos suggests healthy snacking: “We can make a conscious effort to curb our hanger by consuming small portions of nutrient-dense foods throughout the day. Investing in smart habits will help stave off these undesirable symptoms.”