B1: Shizuka, Busy Student in Tokyo

The Explanation

Shizuka stayed up late to finish homework. She finally slept, but her sleep was light. At 6:30 a. m. , her alarm rang. She hit snooze two times. She skipped breakfast because she was late. Outside, she walked fast to the station, but she did not look at the morning sky.

In simple words, a hormone is a message in your body. One part of the body sends it, and another part receives it. Then your body changes something, like energy, mood, or hunger. Hormones do not work alone. They work like coworkers. When one coworker changes their job, other coworkers must adjust.

Your body also uses feedback. Feedback means the body checks results and then changes the next message. If your body notices you are tired, it may send signals to keep you alert. If it notices you ate sugar, it may send signals to lower blood sugar. This is usually helpful. But when life gets messy, the feedback can create problems.

After a short night, Shizuka’s body acted like a small emergency was happening. Cortisol is a stress hormone. It helps you wake up and focus. That is good in the morning. It is also useful when you need to move fast. But if cortisol stays high for too long, you can feel tense. You may also feel tired in a strange way, like your body is running, but your mind is slow.

By late morning, Shizuka tried to study in the library. She stared at one page for ten minutes. Dopamine is connected to motivation and reward. It helps you start tasks and feel interest. When stress stays high, dopamine can feel weaker. Then even easy work can feel heavy. Shizuka did not feel lazy. She felt blocked, like the “start” button was missing.

At lunchtime, another part of the chain showed up. Insulin helps move sugar from your blood into your cells. After poor sleep, the body can become less sensitive to insulin. That means insulin does not work as well as usual. Blood sugar can rise more after a meal. Then it can drop later. Shizuka ate a sweet bread and a coffee drink. At 2 p. m. , she felt hungry again. She wanted another sweet snack, not rice or vegetables.

Now think about mood. Serotonin is a brain signal connected to calm and steady feelings. Sleep, food, and sunlight can affect it. Shizuka noticed she was snapping at her friend. A small joke felt like an insult. Nothing terrible happened. Her body was just less stable, so her emotions moved faster.

Light also mattered in her story. Melatonin is the sleep hormone. It rises in the evening and helps your body get ready for rest. Morning light helps set your body clock, also called your circadian rhythm. When you get outdoor light soon after waking, your body learns, “This is morning. ” Then melatonin can rise at a better time at night. Shizuka stayed indoors all morning, so her clock got a weaker signal.

Exercise can change this chain, but timing matters. A hard workout can raise cortisol for a short time. That is normal. Over weeks, regular movement often improves sleep and insulin sensitivity. Even a 20-minute walk can help some people feel calmer later. For many women, the menstrual cycle can also change sleep, appetite, and mood. Estrogen and progesterone rise and fall across the month. So Shizuka’s “bad day” could be sleep stress plus a normal cycle change.

On Wednesday evening, Shizuka tried a small experiment. She ate a simple breakfast with protein. She took a ten-minute walk outside after waking. She drank water before coffee. She also went to bed at the same time. The next day, she still had work and stress. But she felt more in control. The lesson is not “one hormone equals one problem. ” The lesson is the chain. If you spot the first change, you can often predict the next one.

Practice