That ‘hangry’ feeling you get when you’ve waited too long between meals isn’t all in your head – it’s in your metabolism.
The body runs on fat and glucose – simple carbohydrates that contain a single sugar.
The feeling of hunger is an alert that our blood is getting low on glucose; weakness, light-headedness and shakiness are all symptoms of very low blood sugar, or hypoglycemia.
Feeling ‘hangry’ is a symptom, too – and the latest research on the phenomenon from the University of Guelph suggests that grouchiness may signal a much deeper connection between mood and meal times.
The latest study on the subject wasn’t really intended to be a study on hangriness at all.
It began as part of a wide network of Canadian scientists who are working to better understand depression.
They are attempting to examine depression from many angles, and senior study author Dr Francesco Leri and his team at the University of Guelph wanted to be sure to consider the relationship between sugar, the brain’s reward system and metabolic stress.
Dr Leri and his team had observed that there are higher rates of depression among people with metabolic disorders, such as diabetes.
So, they wondered if the converse might be true: that metabolism could be involved in mood disorders.
To work this out they simulated hunger in mice by giving them an injection of a drug that kept them from being able to metabolize glucose, simulating hunger.
It didn’t take long for the mice’s behavioral changes to start.
The research team saw two main shifts in behavior. The mice became low-energy and sluggish, appearing to have a hard time moving.
Importantly, each mouse had an enclosure with two rooms. The animals were accustomed to getting injections in either room, but the researchers made sure to shut them in one side of their home while receiving the hunger-simulation injection.
‘We measured where they spend more time, and the animals showed a significant aversion to where they received the [injection],’ says Dr Leri.
‘That tells you that it was a negative experience and they’er staying away from that experience.’
He insists that since the animals also received shots – just not of the glucose-blocker – in the other room, that it was not a response to the sensation of an injection, but to the low blood sugar the particular shot induced.
Additionally, the team, led by graduate student Thomas Horman, measured the levels of the mouse version of the stress hormone, cortisol, in the hungry, sluggish mice.
That was up, too.
So what the mouse were experiencing ‘looks like a threat response, by being introduced to something very anxiety-provoking,’ Dr Leri says.
And its behavior is is akin to the anxiety and aggression that we humans display when we’re hangry about being deprived of food.
To test the mood-metabolism link a step further, the University of Guelph team decided to see if they could treat mood symptoms of a metabolism problem with a drug for mood problems: an antidepressant.
When they gave the mice bupropion, commonly used to treat depression, and smoking cessation, ‘aversion for environment was very much gone and stress response was diminished, almost completely,’ said Dr Leri.
‘That told us we were dealing with central mechanisms beyond glucose being available to muscles.
‘So it crosses nutrition with mental health [and shows]nutrtion can play a role in behavior and mood,’ says Dr Leri.
He says that what we see as getting hangry should also be a wake up call to ‘pay attention’ to how what we eat can affect our moods in a broader sense.
For the extremely hangry who ‘experience those mood swings that in some cases can be quite profound, suggesting that they’re experiencing a true biological response, there may be some solution along the lines of a pharmacological therapy,’ says Dr Leri, though of course changing diet is always easier and better if sufficient.
‘But in some forms of clinical depression, nutrition may play a very significant role,’ he adds.