Why is it so easy to lash out at people we love or get downright angry over little stuff, just because we’re hungry? And why do we try to grind through the day, ignoring our hunger, when we could easily grab a simple, healthful snack? What is really going on inside? Why does hunger create wild mood swings?
The very simple, basic answer is that when we’re hungry, our blood sugar drops—sometimes dramatically. And low blood sugar can make us more aggressive. It’s a normal, natural biological response. In caveman times, becoming more aggressive when hungry was a good thing. It prompted you to jump in and fight a pack of animals or other humans for your share of a meal. Back then, hangry people were often more likely to survive. But these days, as you will learn soon, hanger is much more complicated than a drop in blood sugar: it is a complex interplay of hormones, various functions in the body, and psychology.
If I had a magic wand, one of the many things I would do would be to poof away the critical words people say about themselves and their eating. Things like, “How could I have been so stupid to eat that? I didn’t really want to.” Or “I knew I shouldn’t have ordered another brownie. I am an idiot.”
I don’t have a magic wand to make this happen. But I do have some pretty solid information that shows hanger is not usually a personal failure. More often, it’s a result of pure biology!
When you think about what is going on below your skin, you begin to understand why hanger happens so often and why it is important to stay ahead of it. Hanger is a totally normal and natural response, driven by a number of biological factors. Here, I will explain three of the most prominent ones: imbalances in your blood sugar, the stress hormone cortisol, and a pesky neuropeptide that impacts your desire to eat.
The first trigger of hanger is a fluctuation in blood sugar, also known as blood glucose. When you eat, your body takes the macronutrients from food—proteins, fats, and carbohydrates—and breaks them down into smaller compounds—mostly amino acids, fatty acids, and simple sugars. These compounds are then distributed throughout our bodies to give us all the energy that powers everything from basic needs, such as breathing, to more intense activities, such as running six miles or taking an exam. When you haven’t eaten in a while, your blood-glucose levels dip and your body isn’t getting what it needs to function well.
Since glucose is the main energy source for our body, it’s easy to see how a lack of it can lead to fatigue, irritability, and trouble concentrating—especially when you’re still trying to burn through a busy day. The longer we wait between meals, the less glucose circulates in our bloodstream—and the less fuel our body has to function. It’s like trying to run a car without any gas.
The brain works best when it is fed, because it needs glucose to function. But it isn’t just the amount of glucose that’s important. Where the glucose comes from matters, too. Consuming chocolate or a cupcake leads to a sudden surge of energy-boosting sugar. But it doesn’t last long. That’s because the simple sugars found in chocolate and cupcakes release glucose into the bloodstream very quickly. They provide around twenty minutes of alertness. Then the sudden, high level of sugar runs its course, our blood-glucose levels crash, and we can be left anxious and unable to focus.