Food, your mood and how we choose

Get short tempered before lunch? Snap at people if you’ve skipped breakfast? Perhaps you are suffering from hanger – the combined effects of hunger and anger.

Self-control requires energy. When our energy levels are low, it follows that our control over our temper is reduced too.

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As blood glucose levels drop, the stress hormones cortisol and adrenaline are released to drive us to find our next meal. Along with a chemical identified as neuropeptide Y, these combine to make people more aggressive to those around them.

The effects of blood sugar on aggression were measured in a 2014 trial investigating 107 married couples. In the first part, the couples used voodoo dolls and up to 51 pins to express the level of anger that they felt at their partner at that time, and the blood glucose levels of both was measured.

In the second half, the couples played a competitive game, after which the winner could blast the loser with a loud noise through a set of head-phones. As expected, the lower the blood glucose, the more pins and the longer the noise the partners received.

A 2012 study at Columbia University looked at case sentencing by judges and saw they tended to be more lenient first thing in the morning and right after lunch. On the other hand, this may have been more to do with the ordering of the caseload (shorter cases vs longer and more complicated ones) than the timing of meals.

The hunger hormone, ghrelin, which is produced in the stomach prior to meals and during fasting, has been seen to have a negative impact on the brain’s ability to make rational decisions. During an experiment at the University of Gothenburg in 2016, rats with a higher level of ghrelin (mimicking hunger conditions) behaved more impulsively and erratically.

However this study was done in rats, they can be a good model for humans, and more research is needed to confirm the effect is true in us. But perhaps for now be careful when making decisions on an empty stomach.