Zeina's Book of Whys

We get tired because of several factors that affect our body's energy levels and overall functioning. Here's why:

ENERGY DEPLETION
Our body uses energy from food (mainly glucose) to fuel its activities. As we go through the day, we burn through that energy. Once our energy reserves are used up, we start feeling tired as our body signals that it needs to replenish itself.

PHYSICAL ACTIVITY
When we engage in physical activities, our muscles use up energy and create waste products, like lactic acid. The build-up of these waste products and the depletion of energy stores makes us feel fatigued. Rest allows our body to recover and repair itself.

SLEEP CYCLE
Sleep plays a huge role in helping us recharge. During the day, our body and brain accumulate a substance called 'adenosine', which makes us feel sleepy and tired. Sleep helps clear out this buildup and restores our energy, so we wake up feeling refreshed.

MENTAL FATIGUE
Mental exertion, like thinking, concentrating, or problem-solving, also uses up energy. The brain consumes a lot of glucose, and over time, the mental effort leads to tiredness as well.

CIRCADIAN RHYTHM
Our internal clock (circadian rhythm) regulates our sleep-wake cycle. This rhythm causes us to naturally feel more tired at certain times of the day, like late at night or in the afternoon, as our body prepares for rest.

HORMONES AND STRESS
Hormones like cortisol help us stay alert, but when we experience chronic stress, cortisol levels can become disrupted, leading to feelings of exhaustion and fatigue. Similarly, lower levels of certain hormones, like melatonin (which helps with sleep), can contribute to tiredness.

In short, tiredness is your body's way of telling you it needs rest, recovery, or more fuel!