Hangry: is it real? Why hunger can make you grumpy

Your stomach growls. A friend asks you a simple question, and somehow your answer comes out sharper than you meant. A few bites of lunch later, you feel like yourself again.

There is a word for this: hangry, a mix of “hungry” and “angry.” As a 2022 paper by Viren Swami and colleagues notes, the word has entered everyday English. But is being hangry real, or just a handy excuse? Scientists have started to look.

Catching hanger in everyday life

Much of the earlier research on hunger and mood was done in the lab. Swami, Samantha Hochstöger, Erik Kargl and Stefan Stieger wanted to catch hanger out in the wild.

They recruited 64 adults from Central Europe, mostly from Austria and Germany. For 21 days, a smartphone app pinged them five times a day. Each time, they rated how hungry, angry and irritable they felt, how pleasant or unpleasant they felt, and how worked up, or aroused, they were. Three of the pings came at 8 a.m., noon and 6 p.m., before typical mealtimes, when hunger was likely to be high. Altogether, the volunteers sent in 9,142 answers.

The pattern was clear. When people felt hungrier, they also reported more anger and irritability, and less pleasure. This held even after the researchers took into account sex, age, body mass index, eating habits and how prone to anger each person was in general. Both a person’s hunger in the moment and their average hunger over the three weeks went along with grumpier feelings. Hunger was not significantly linked to arousal, though.

The team is open about what the study can’t tell us. It did not record what situations people were in, it used a single question each for anger and irritability, and it did not measure hunger in the body, such as blood sugar or hunger hormones. The volunteers were also mostly women, about 81%, and were not a representative sample, so the authors call for repeating the study with more representative and more diverse groups.

A hard lesson from history

Long before anyone said “hangry,” scientists saw what serious hunger can do to people. During World War II, 36 conscientious objectors took part in a study of semistarvation led by Ancel Keys at the University of Minnesota. The aim was to understand the physical and psychological effects of starvation, and how to help civilians who had starved during the war recover.

Leah Kalm and Richard Semba retold the story in 2005. Most of the men lost more than a quarter of their body weight. Many had anemia, fatigue, apathy, extreme weakness, irritability, nerve problems and swelling in their legs. In 2003 and 2004, 18 of the original 36 were still alive and were interviewed. Despite the suffering, and the ethical questions about starving healthy people, all of them said they would do it again.

That was nothing like a late lunch, of course. But irritability was right there on the list.

Hunger needs a story

So hunger and grumpiness often travel together. Does that mean hunger makes every moment worse? A 2019 study by Jennifer MacCormack and Kristen Lindquist suggests that hunger alone is not enough to make someone hangry.

Their idea is that people feel hunger as emotion when they read their body’s feelings as strong, unpleasant emotions, and especially when the setting is a negative one. In two studies, hungrier people saw ambiguous pictographs as more negative, but only in a negative context, not in a neutral or positive one. In a third study in the lab, hunger caused people to feel negative emotions and to judge a researcher more harshly. But this only happened when people were not aware that they were treating their body’s feelings as emotions.

Swami’s team reads their own results in a similar way. In their data, hunger went along with feeling less pleasant. Everyday cues, such as dealing with other people, heat or even being asked to fill in a survey, may then help turn that low feeling into “I’m angry” or “I’m irritated.” Hunger may not automatically lead to bad moods, they write, but it may not take much for hungry people to feel anger and irritability.

A message from your stomach

Where does the hungry feeling come from? One messenger is ghrelin, a hormone made mainly by the stomach. In 2001, David Cummings and colleagues took blood from 10 healthy people 38 times over 24 hours, while serving them meals on a fixed schedule. Ghrelin rose nearly twofold just before each meal and fell to its low point within an hour after eating. In rodents, high doses of ghrelin switch on a group of hunger neurons in the hypothalamus and make the animals eat more. The team saw the rise before meals as support for the idea that ghrelin helps start meals in humans.

At least in rats, ghrelin may do more than make us peckish. In a 2016 study, Rozita Anderberg, Karolina Skibicka and colleagues trained rats on three tests of impulsive behavior and choice. When ghrelin was delivered into the rats’ brains, they became more impulsive. They pressed a lever during periods when they were supposed to hold back, and they less often chose a large reward that came with a wait. Blocking ghrelin’s receptors in the brain made them less impulsive. Ghrelin given into the ventral tegmental area, a region that holds dopamine cells, was enough on its own to raise impulsivity.

Impulsive is not the same as angry, and rats are not people. Still, it hints that a hunger hormone can reach beyond appetite.

The hunger neurons that feel bad

In the hypothalamus sits a group of hunger neurons named after a molecule they make, agouti-related peptide, or AgRP for short. Switching them on makes a mouse eat. But what does their activity feel like to the mouse?

In 2015, J. Nicholas Betley, Scott Sternson and colleagues set out to test this. Well-fed mice tasted one flavor while their AgRP neurons were switched on with light, and another flavor without. Afterward, the mice liked the first flavor less. Hungry mice showed the mirror image: they came to prefer a chamber where their AgRP neurons had been quieted. So AgRP activity is something mice would rather avoid. Scientists call this “negative valence.”

It was not like nausea, and it was not strongly unpleasant like a shock. The researchers describe it as a teaching signal. When the signal fades, the mouse learns which flavors and places go with food.

The team also watched these neurons in hungry mice through a tiny head-mounted microscope. AgRP activity dropped fast when food arrived, and even when a cue that predicted food appeared. When the mice got a fake pellet instead, the activity bounced back. Keeping the neurons quiet took real nutrients.

In the same year, Yiming Chen, Zachary Knight and colleagues reported something similar. In hungry mice, simply sensing food was enough to rapidly flip the state of AgRP neurons, before a single bite. The size of the change depended on how tasty the food was and on how well fed the mouse was.

Betley’s team noted that this unpleasant signal fits with how people describe hunger and thirst, as negative feelings. They also point out that AgRP circuits are found in humans, too.

Hungry mice pick fewer fights

Here is a twist. If hunger feels bad, do hungry animals fight more? Not always.

In 2016, Stephanie Padilla, Richard Palmiter and colleagues used a classic test of territory. They placed a younger male mouse into the home cage of a male who lived there. Resident males that had fasted for 48 hours were less aggressive toward the newcomer than fed residents, and a 24-hour fast had the same effect. Instead of fighting, the hungry residents spent more time sniffing the newcomer’s snout, perhaps smelling food on it, the authors suggest. They also reared up and jumped as if trying to escape.

Switching on AgRP neurons in well-fed residents also made them less aggressive. And when food was offered during the test, those mice spent most of the time eating.

The team traced part of this effect to AgRP neurons that reach the medial part of the amygdala, which in turn connects to an area called the bed nucleus of the stria terminalis. Their explanation goes like this. Hungry animals will fiercely defend scarce food. But when the food has run out, guarding an empty territory wastes energy, and finding food matters more. They propose that AgRP neurons act as a master switch, helping an animal choose what to do based on its body’s state and its surroundings.

So even in mice, hunger is not a simple “angry” button. What it does depends on the situation.

What about blood sugar?

A popular explanation for hanger is low blood sugar. In a 2014 study, Brad Bushman and colleagues measured blood glucose in 107 married couples for 21 days. Each evening, participants stuck between 0 and 51 pins into a voodoo doll that stood for their spouse, depending on how angry they were with them. Later, in the lab, the couples played a 25-round contest in which the winner blasted the loser with loud noise through headphones. The lower people’s glucose, the more pins they used, and the louder and longer the noise they set for their spouse.

Bushman’s team linked this to the idea that self-control runs on energy from glucose. In a 2014 commentary, Florian Lange and Robert Kurzban pushed back. That glucose model of self-control, they wrote, has run into problems in theory and in replication studies. The voodoo study did not measure self-control at all: the doll was a single self-report of how angry people felt. And the noise result used each person’s average glucose over three weeks. That works more like a personal trait, which could be tied to aggression through other factors such as age.

Even so, Lange and Kurzban wrote that they do not doubt hungrier organisms are more aggressive. Their point was about the explanation, not the everyday experience. Swami’s team adds that larger, stronger studies of the self-control idea have produced mixed results.

So, is hangry real?

Here is where the science stands. In everyday life, hungrier moments went along with more anger and irritability, at least in the one group of volunteers studied so far. In the lab, hunger pushed feelings in a negative direction, but mainly in a negative setting and when people were not aware they were reading their body’s feelings as emotions. And in mice, hunger signals from the hypothalamus carry an unpleasant edge, and they steer behavior in ways that depend on the situation, sometimes even calming a fight.

So hangry seems to be real, but it is not a simple switch. It looks more like a grumbly body feeling meeting a bad moment, with the brain filling in the rest. Next time your stomach rumbles and the whole world seems extra annoying, it might be worth a gentle question: is it them, or is it lunch?

#hangry #hunger #emotions #hypothalamus #everyday brain

Sources

1. Hangry in the field: an experience sampling study on the impact of hunger on anger, irritability, and affect. Swami V, Hochstöger S, Kargl E, Stieger S. PLOS ONE 17, e0269629 (2022)
2. Feeling hangry? When hunger is conceptualized as emotion. MacCormack JK, Lindquist KA. Emotion 19, 301–319 (2019)
3. They starved so that others be better fed: remembering Ancel Keys and the Minnesota experiment. Kalm LM, Semba RD. The Journal of Nutrition 135, 1347–1352 (2005)
4. A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Cummings DE, Purnell JQ, Frayo RS, Schmidova K, Wisse BE, Weigle DS. Diabetes 50, 1714–1719 (2001)
5. The stomach-derived hormone ghrelin increases impulsive behavior. Anderberg RH, Hansson C, Fenander M, et al. Neuropsychopharmacology 41, 1199–1209 (2016)
6. Neurons for hunger and thirst transmit a negative-valence teaching signal. Betley JN, Xu S, Cao ZFH, et al. Nature 521, 180–185 (2015)
7. Sensory detection of food rapidly modulates arcuate feeding circuits. Chen Y, Lin YC, Kuo TW, Knight ZA. Cell 160, 829–841 (2015)
8. Agouti-related peptide neural circuits mediate adaptive behaviors in the starved state. Padilla SL, Qiu J, Soden ME, et al. Nature Neuroscience 19, 734–741 (2016)
9. Low glucose relates to greater aggression in married couples. Bushman BJ, DeWall CN, Pond RS, Hanus MD. PNAS 111, 6254–6257 (2014)
10. Sugar levels relate to aggression in couples without supporting the glucose model of self-control. Lange F, Kurzban R. Frontiers in Psychology 5, 572 (2014)