It's happened to every single one of us: you've accidentally missed lunch and, more often than not, you're doing something semi-annoying like food shopping or running errands, and all of a sudden an angry, stroppy beast takes over you.
Petty fights with your significant other or friend ensue, and it's not until you stuff your face with a burger do you realise how stupid it was to get enraged over him getting muesli not toasted muesli. GEEZ.
'Hanger' is how we describe the way we act when we're overly hungry, but why does this occur?
"It's actually quite an interesting concept," Zane Andrews -- an associate professor of physiology and neuroscientist who studies how food (and lack of food) affects the brain at Monash University -- told The Huffington Post Australia.
"In the brain we have neurons that will actually tell us to eat, and obviously when you eat, that is a sense of fulfillment and those neurons turn off. However, if we don't immediately have food those neurons will persistently fire and they will also engage other parts of the brain that regulate things like anxiety and mood.
"This is where the anger or 'hanger' comes into it. We say 'hanger' but it's probably a whole mishmash of things like anxiety and grumpiness, not aggressive anger per se."
Interestingly, instead of our brain kindly telling us "mate, you're hungry, maybe eat something", it says "mate, if you don't eat soon, shit's about to go down".
"When we haven't eaten in a while and these hunger neurons turn on and drive motivation for food, the normal response is to eat to fulfill that need, but we also know that if these neurons persistently fire, it motivates us to eat not through positive reinforcement, but through negative reinforcement," Andrews explained.
"That means they create an uncomfortable feeling of aversion, and the reason we're motivated to feed is to remove that feeling. To remove that hanger, one might say."
Low blood sugar levels have a lot to do with hanger, as they are one of the key feedback signals to tell your brain you're hungry and to make your 'hungry' neurons keep firing.
"[Blood sugar levels] is probably one of the key components because the way these neurons sense hunger, in many respects, is a coordinated detection of nutrient signals and hormonal signals feeding back to the brain," Andrews told HuffPost Australia.
"The key nutrient signal in the body is essentially glucose and the body will fight to maintain blood glucose. This is probably the number one thing the body does to keep alive.
"The lower the blood glucose gets, the more active these hunger neurons in the hypothalamus (a part of the brain that regulates subconscious things like thirst, reproduction and food intake) get. Over a long period of time, those neurons get more active and then project into parts of the brain that are going to engage those anxious, mood, aversive type of feelings."
Accredited practising dietitian Jemma O'Hanlon agrees, saying feeling hangry is simply a way of our brains telling us we're in need of a carbohydrate boost.
"Glucose, a simple sugar which is found in carbohydrate-containing foods, is the preferred fuel source for the brain," O'Hanlon told HuffPost Australia.
"When we're not feeding our brains enough fuel, our moods changing are a major symptom, so it's really important that we feed our brains by eating regularly and providing them with the right type of fuel.
"If we don't provide them with regular energy boosts, they can go a little haywire. The result is often what we term 'hangry'. This is our brain sending us a clear message. It's a bit like a dog who doesn't leave your feet at the end of the day -- it needs to be fed!"
If you do find you are very hungry and feeling anxious, accredited practising dietitian Kathryn Hawkins says the best thing to do is recognise this and the need for a nutritious snack.
"Good choices are some cheese and crackers, nut butter on wholegrain toast, dried fruit and nuts, a milk based drink or smoothie," Hawkins told HuffPost Australia. "Try to have the appropriate portion and make sure you have a big drink of water, too."
"Eat regularly," O'Hanlon added. "Make sure you kick start your day with a healthy breakfast and eat regular meals throughout the day. It's often when we've skipped a meal or gone a long time between meals that we get hangry."