Jordan Gaines Lewis, Ph.D.

Brain Babble

Why Do We Get "Hangry"?

Here are 3 reasons why some of us get angry when we're hungry.

Posted Jul 06, 2016

Niklas Hellerstedt (Flickr)
Source: Niklas Hellerstedt (Flickr)

One lovely fall day a few years ago, my now-husband (I'm not sure why he married me after this) almost left me on the side of the road. We had just left a Penn State football game, and I was H-U-N-G-R-Y.

My resulting behavior was far from what you might consider "ladylike," much less "civilized." I won't even re-type the words that were spoken. Eventually, a pit stop for a burger and fries managed to tame my inner beast.

What causes the sensation of "hanger" – the phenomenon of feeling angry and short-tempered when hungry? 

Three major factors are thought to contribute to our bad tempers when we're famished:

1. When we eat, carbohydrates are broken down into simple sugars, one of which is glucose. Right after a meal, the levels of glucose in our blood are high.

Mikael Häggström (Wikimedia Commons)
Glucose metabolism.
Source: Mikael Häggström (Wikimedia Commons)

Over time, though, blood-glucose levels drop. Eventually, if these levels fall far enough, your brain will perceive it as life-threatening. Unlike other organs, which have an energy back-up, your brain relies solely on glucose as a fuel source and requires a continuous supply. In fact, despite accounting for only 2% of your body's mass, your brain is estimated to use up 20-23% of your body's energy intake throughout the day, even at rest. Low blood glucose, obviously, signals, "imminent death! Act now!"

2. To our other organs, low glucose ramps up hormones that act to increase glucose in the body. Among these are epinephrine and cortisol, which are synthesized in the adrenal glands. These are both stress hormones, released when our body perceives threat, like a lion chasing us or an organic chemistry exam being handed out in class. That's enough to change someone's mood for the worse, right?

3. As it turns out, anger and hunger don't only share many of the same letters, but they're also controlled by similar genes.

One of these genes produces a protein called neuropeptide Y, which not only stimulates eating behavior, but also regulates anger and aggression. Long story short, I probably had pretty high levels of neuropeptide Y after that football game.