Why Do We Get Hangry?

The clock strikes one in the afternoon. The meeting was supposed to wrap up an hour ago. Breakfast was skipped, and lunch is delayed. Someone asks a well-meaning question. As glucose drops, the brain’s patience reserve dwindles, stress hormones spike, and small inconveniences begin to induce rage. What might seem like a bad mood is, in fact, a biological alarm system: hunger sharpening into anger, better known as being hangry.

The complex, yet common, link between hunger and emotions is evident across scientific literature and popular culture. In the well-known advertisements for the Snickers candy bar, protagonists turn into annoyed or furious characters when famished, while the brand’s tagline reads “you’re not you when you’re hungry.” Similar to this fictional portrayal, scientists have documented and analyzed hanger in multiple scenarios.

Is It Really Hanger?

In 2011, researchers at Tel Aviv University analyzed how a judge’s hunger levels affected the leniency of the sentences they gave out.¹ They analyzed 1,112 parole hearings over 10 months and observed that the percentage of favorable rulings dropped from 65 percent to almost zero as mealtimes neared. The numbers bounced back once the judges returned with a belly full of food. While the study sparked the usage of the term “the hungry judge effect” to explain the consequences of hanger, researchers found that other variables such as mental fatigue or the judges’ choice to keep certain cases towards the end of sessions could explain the results.

Since then, researchers have conducted more experiments to methodically determine if hunger pangs really do make people more irritable. In 2022, psychologists at Karl Landsteiner University of Health Sciences examined 64 participants over three weeks and recorded their hunger, anger, pleasure, and arousal at five timepoints each day.² The individuals who reported greater hunger also felt more anger and less pleasure.

Hanger, Historically

Until about a decade ago, many psychologists assumed that hunger influenced emotions and behavior by impairing self-regulation and making a person more impulsive.³ They hypothesized that a drop in blood glucose—which occurs in anticipation of large meals—makes it difficult to modulate energy-intensive processes such as emotion control. Researchers analyzed this link in detail in 107 married couples over three weeks.⁴ They asked the participants to stick needles into voodoo dolls that represented their spouse or blast them with loud sounds. Those with lower glucose levels stuck more pins into the dolls and punished their partners with blaring sounds. However, conflicting results and failed replications have debunked the theory linking low blood glucose to impaired emotional regulation.⁵

An alternative explanation for hanger lies in the physiology of hunger itself. One of the key hormones that signals hunger is ghrelin. Predominantly secreted by the stomach, this 28-amino-acid peptide triggers the release of arousal hormones like cortisol and adrenaline.⁶ “When blood glucose starts to get low, the brain predicts that you need to update them, which induces a cascade of different hormones and neuropeptides that signal hunger sensations,” said Kristen Lindquist, a psychologist at The Ohio State University who studies how states of the body contribute to emotions. “These induce approach-related behavior that could help you go out and get food.”

Sweeping Effects of the Hunger Hormone

But signaling hunger isn’t where their effects end. “All of these hormones are also involved in emotion,” Lindquist said. In fact, brain imaging of hungry humans showed activation of emotion regulatory regions like the amygdala, insula, and cingulate cortex.⁷ “So, it's not that surprising that there is a strong link between these states that historically psychologists, neurologists, and physiologists have thought of as distinct,” she added.

Hunger increases aggression and impulsivity in other animals as well, such as flies, beetles, meerkats, chamois, and rats.^8–11 Taking advantage of these similarities, various groups have analyzed the effects of ghrelin on behavior in model systems. When scientists injected the hunger hormone into rats, the rodents reacted more to a stimulus that was designed to withhold their responses, indicating that the peptide enhanced impulsiveness.¹² The team saw the opposite effect when they blocked ghrelin receptors in the rats. In another study, researchers reported that hungry rats who could see and smell food, but couldn’t access it, showed intense biting behavior.¹¹

But how does ghrelin bring about anger? The hormone activates neurons in the hypothalamus—a brain region crucial to maintaining homeostasis—and leads to the release of neuropeptide Y, a potent appetite-stimulant.¹³ Researchers also speculated that the peptide is a regulator of aggression. To test this, scientists measured neuropeptide Y levels in the cerebrospinal fluid of healthy individuals, as well as those with explosive anger personality disorder.¹⁴ The latter group had higher levels of the peptide compared to the former.

When Hunger Becomes Hanger

Though there’s a mechanistic link between hunger and mood, Lindquist thinks that rather than hunger driving anger, hunger makes a person view the world more negatively. To test this theory, she asked study participants (hungry or full) to look at negative, positive, or neutral emotional images, followed by an ambiguous one such as a Chinese character.¹⁵ The hungry individuals who saw negative images viewed the character as unpleasant. The perception of the two hungry groups who saw positive and neutral images did not differ from those of satiated individuals.

To determine if people could refrain from hunger influencing their moods, Lindquist conducted another experiment where she asked participants (again, hungry or full) to write a story either focusing on their emotions or not.¹⁵ Then, they all faced a frustrating situation meant to irritate them. The hungry people who did not concentrate on emotions reported feeling hangrier than those who did.

According to Lindquist, the findings suggest that reflecting on one’s emotions helps a person look at a situation objectively. “Instead of having that negative feeling bound to the situation, they were able to say, ‘wait a second, is this just me feeling sort of irritated? And therefore, I'm not going to take it out on someone,’” she said. She believes that people who are more aware of their emotions and understand where they're coming from, show better self-regulation.

The link between hunger and emotions is also evident in people with eating disorders like anorexia nervosa or bulimia, though different from the norm. Researchers reported that certain individuals with anorexia nervosa found hunger pleasurable.¹⁶ “We are just scratching the surface of how the gut relates to the brain,” Lindquist said. “We hope to discover new important ways that people can take care of their physical self and in turn, help their mental self.”