This post is also available in Dutch.
It is dinnertime. You feel your stomach growling, but you still have to travel home. Suddenly you are annoyed by anyone that is walking slowly in front of you…. and, why are those people on the train speaking so loudly? Do you recognize this? You are surely not alone in this. This phenomenon is so common that there is even a word for it: hangry, a combination of hungry and angry. But can hunger really influence your mood, and if so, how does that work?
A short temper because of low blood sugar
It all starts with your blood sugar level. Glucose is fuel for the body and approximately 25% is used as fuel for our brain. When you eat little, this level drops and your brain will therefore have less energy. No wonder that hunger influences the functioning of your brain.
And indeed, this was also shown in a remarkable American study: blood sugar levels of couples were measured continuously for 21 days and they were asked to put pins into a voodoo doll when they were angry at or got annoyed with their partner. As it turned out, participants with lower blood sugar levels put significantly more pins into the doll than people with higher blood sugar levels. Having low blood sugar levels thus led to more aggression and annoyance.
Less self-control and a survival mechanism
There are probably multiple explanations for this effect. First of all, self-control of emotions and impulses is very energy consuming. When your blood sugar is too low and your brain therefore has less energy, this will come at the cost of regulating your behavior and you will more easily flip out.
Secondly, a low blood sugar level activates the production of adrenaline and cortisol. These hormones are also produced when you are stressed and they activate a survival mechanism in the body: it makes that you immediately start looking for food. These hormones, however, also make you feeling rushed, which then creates this short temper.
Finally, rodent studies that have been carried out, suggest that substances that activate the feeling of hunger in the brain (Neuropeptide-Y and AGRP) also cause an unpleasant or aggressive feeling. Neuropeptide-Y, for instance, activates the amygdala, the brain region involved in emotion regulation. The negative feeling that arises probably works as a “punishment” to motivate you to quickly go find some food.
Neuropeptide-Y is also the reason why some people get hangry more easily than others. Some people just have a genetic predisposition to produce more of this hormone, which makes them more prone to hangry feelings.
Being hangry therefore is the consequence of a survival mechanism that ensures that you do not go hungry. Seen from an evolutionary perspective, this comes in handy, but in our modern world with an excess of food, this is mainly annoying. Therefore, currently there is ongoing research that investigates ways to decrease this feeling; this could for instance help overweight people to lose weight. Currently there is no solution to this feeling yet, so the best you can do for now is to always have a granola bar in your bag for when the hangry feeling strikes again.