Why do we sleep?
A lot is still unknown about the purpose of sleep. However, it’s widely accepted that there isn’t just one explanation for why we need to sleep. It’s likely necessary for many biological reasons.
To date, scientists have found that sleep helps the body in several ways. The most prominent theoriesTrusted Source and reasons are outlined below.
Energy conservation
According to the energy conservation theory, we need sleep to conserve energy. Sleeping allows us to reduce our caloric needs by spending part of our time functioning at a lower metabolism.
This concept is backed by the way our metabolic rate drops during sleep. Research suggests that 8 hours of sleep for human beings can produce a daily energy savings of 35 percentTrusted Source over complete wakefulness.
The energy conservation theory of sleep suggests that a main purpose of sleep is to reduce a person’s energy use during times of the day and night, when it’s inconvenient and less efficient to hunt for food.
Sleep is essential for good health. In fact, we need sleep to survive — just like we need food and water. So, it’s no wonder we spend about one-third of our lives sleeping.
Many biological processes happen during sleep:
The brain stores new information and gets rid of toxic waste.
Nerve cells communicate and reorganize, which supports healthy brain function.
The body repairs cells, restores energy, and releases molecules like hormones and proteins.
These processes are critical for our overall health. Without them, our bodies can’t function correctly.
Let’s take a closer look at why we sleep, along with what happens if we don’t get enough.
Emotional well-being
Similarly, sleep is necessary for emotional health. During sleep, brain activity increases in areas that regulate emotion, thereby supporting healthy brain function and emotional stability.
Areas of the brain in which sleep increases activity include:
amygdala
striatum
hippocampus
insula
medial prefrontal cortex
One example of how sleep can help regulate emotion occurs in the amygdala. This part of the brain, located in the temporal lobe, is in charge of the fear response. It’s what controls your reaction when you face a perceived threat, like a stressful situation.
When you get enough sleep, the amygdala can respond in a more adaptive way. But if you’re sleep-deprived, the amygdala is more likely to overreact.
Research shows that sleep and mental health are intertwined. On the one hand, sleep disturbances can contribute to the onset and progression of mental health issues, but on the other hand, mental health issues can also contribute to sleep disturbances.
Weight maintenance
Sleep affects your weight by controlling hunger hormones. These hormones include ghrelin, which increases appetite, and leptin, which increases the feeling of being full after eating.
During sleep, ghrelin decreases because you’re using less energy than when you’re awake.
Lack of sleep, however, elevates ghrelin and suppresses leptin. This imbalance makes you hungrier, which may increase the risk of eating more calories and gaining weight.
Recent research shows that chro
Cellular restoration
Another theory, called the restorative theory, says the body needs sleep to restore itself.
The idea is that sleep allows cells to repair and regrow. This is supported by many important processes that happen during sleep, including:
muscle repair
protein synthesis
tissue growth
hormone release
Brain function
The brain plasticity theory says sleep is required for brain function. Specifically, it allows your neurons, or nerve cells, to reorganize.
When you sleep, your brain’s glymphatic (waste clearance) system clears out waste from the central nervous system. It removes toxic byproducts from your brain, which build up throughout the day. This allows your brain to work well when you wake up.
Research suggests that sleep contributes to memory function by converting short-term memories into long-term memories, as well as by erasing, or forgetting, unneeded information that might otherwise clutter the nervous system.
Sleep affects many aspects of brain function, including:
learning
memory
problem-solving skills
creativity
decision making
focus
concentration
