Why Do We Get Grumpy When We’re Hungry?

If you know anyone who gets grumpy when they’re hungry then you’ll know just what a sudden personality change this can bring on. Perfectly nice and reasonable people have been known to become suddenly mean and vindictive at the blink of an eye and sometimes this can severely test friendships and relationships. Once you work out that your friend has this reaction to hunger though it’s okay – you just need to get some crackers in them when you see them start to turn into the Incredible Hulk and the crisis can be averted.

Other people don’t get angry when they’re hungry but instead become nervous and anxious. This is how it affects me personally. When I’m deep in work sometimes I will notice myself becoming gradually paranoid and scared of everything, while also shaking a little bit and struggling to concentrate. Eventually I’ll realise I haven’t eaten for several hours and I’ll have a banana to put everything right with the world again.

The availability of quick-fixes not withstanding though, this is still something of a problem and it’s also pretty weird when you think about it. Why should being hungry have this effect on us?

Chemical Explanations

Actually there are a number of things going on here. The principle effect is a dip in our serotonin levels which occurs as we get hungry. Serotonin is a ‘feel good hormone’ in the brain and presumably the dip is intended to signal to the brain that all is not well and that we need to seek some kind of reward (food) in order to get back some of those happy hormones.

One of the roles of serotonin is to help us regulate anger and anxiety among other emotions. The balance then gets a little out of whack and we end up acting unreasonable. For a quick boost in serotonin you should look for bananas, dates, avocados, walnuts or pumpkin seeds.

This drop in serotonin explains why you’re not happy, but the anger side comes from an increase in adrenaline. Recognising that you are starving yourself, your brain will react by producing the stress hormone adrenaline (the fight or flight hormone). This is also the reason that your hands may start to shake. Adrenaline also makes you hyper aware which explains my paranoid tendencies.

Energy Levels

Another point to consider is that our blood sugar level drops when we’re hungry too. Sugar is what our body uses for energy, so without that available glucose we have less ‘power’ for running various functions in our brain and body. This includes the ability to regular our own emotions and to engage the logical parts of our brain, making us more unreasonable and reactionary.


This has interesting implications for dieting, and it’s important to recognise that moodiness may be one of the side effects of reducing your food intake. One study described dieting as leading to an ‘aggressive frame of mind’, while another described avoiding carbs in particular as creating ’emotional zombies’. This could also contribute to the popular stereotype of larger people being ‘jolly’; an abundance of fuel and constant reward ensures that their brains are filled with happiness hormones, while those who are very thin are constantly teetering on the edge of jitters.

So now you know why hungriness makes you jittery, and you’re hopefully a little more aware of how your dieting may be affecting your mood. If you’ve been cranky, irritable or anxious lately, then maybe it’s time to start eating a little more again?

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