The Hungry Organ in Your Head

When you think about which parts of your body consume the most energy, you might imagine your muscles. After all, running and swimming make us tired and hungry. However, one of the hungriest organs in the body is actually inside your head: your brain.

An adult's brain weighs about 1.4 kilograms, which is only around two percent of total body weight. Yet it consumes about twenty percent of the energy the body uses at rest. In other words, this small organ uses far more than its fair share. Scientists say that the brain runs on about twenty watts of power, which is similar to a dim light bulb. That may not sound like much, but it never turns off, even while you are sleeping.

Why does the brain consume so much energy? The answer lies in its tens of billions of nerve cells. They are always sending signals to each other, and every signal needs energy. Most of this energy comes from glucose, a type of sugar carried in the blood. Because the brain cannot store much glucose, it depends on a steady supply from the food we eat.

Interestingly, solving a difficult math problem does not make the brain consume much more energy than usual. Studies show that its energy consumption rises by only a few percent. Most of the brain's energy is used for activity that never stops, even when we are resting. So why do we feel tired after studying for hours? Researchers are still trying to answer this question. The feeling may be the brain's way of telling us to take a break, rather than a sign that its fuel has run out.

What does this mean for students? First, skipping breakfast is not a good idea. Eating breakfast refills your body's energy supply, which may help you focus in morning classes. Second, short breaks are useful. Unlike your phone, your brain does not show its battery level on a screen, so it is wise to listen to it and take care of it every day.