If you've ever felt peckish, you'll know it can start to have an impact on the way you think, and now there's new evidence to back up that feeling because researchers have found that the hormone ghrelin, released by the body before meals, has a negative impact on decision-making and impulse control.
Previous research has shown that your stomach starts to produce ghrelin - informally known as the "hunger hormone" - when you get hungry, and that has an impact on regulating your appetite. Now, for the first time, a team in Sweden has managed to link it to a lack of rational thinking and a loss of impulse control.
In the study, academics from the University of Gothenburg set up an impulsivity test for rats, where they were rewarded with sugar when they correctly followed a signal to either press a lever or leave it alone. Through a repeated series of tests, the rats gradually learned which action corresponded to a reward.
Pressing the lever when signalled to leave it alone was seen as a sign of impulsiveness (like eating a chocolate when dinner is almost ready). When ghrelin was added to the brains of the rats, their impulsiveness increased and vice versa.
"Our results showed that restricting ghrelin effects to the ventral tegmental area, the part of the brain that is a crucial component of the reward system, was sufficient to make the rats more impulsive," said one of the researchers, Karolina Skibicka. "Importantly, when we blocked ghrelin, the impulsive behavior was greatly reduced."
In the same way, the scientists suggest, the presence of ghrelin when we're hungry could be affecting the quality of our own decision-making.
They also found signs that the ghrelin injections in rats also caused changes in dopamine-related genes and enzymes (controlling the reward and pleasure centres of the brain) that are already associated with ADHD ( attention deficit hyperactivity disorder) and OCD (obsessive compulsive disorder).
Further study into the effects of ghrelin could potentially lead to better treatments for these disorders, the researchers suggest.
So we're probably telling you something you already know, but seriously, don't try to make decisions on an empty stomach, because it's probably not good for you. It's just one of many biological processes happening when we start to get stomach pains, and research has also pointed to a tendency to get more short-tempered and less likely to behave within socially acceptable norms (aka 'hangry').
This new study in some ways contradicts findings from a 2014 paper that suggested decision-making was actually improved on an empty stomach, based on experimental exercises carried out with fasting and non-fasting volunteers. In that case, scientists concluded that hunger increases our reliance on our 'gut feeling,' which in certain cases can benefit "complex decisions with uncertain outcomes".
Now, before we get too carried away with either side of the debate, it's important to note that this latest study was conducted on rats, not humans. And while these results could transfer, we won't know until we test the experiment out on humans.
Getting the food we need is so crucial to the survival of the species, it's no surprise that when it's lacking, our internal wiring can shift in certain ways, even if we don't fully understand yet how that shift actually works. In the meantime, perhaps the best course of action is to simply always get a second opinion on any important decisions if you're dealing with a mild case of hanger.
The results of the study have been published in the journal Neuropsychopharmacology.