Why Do We Sleep?

Why Do We Sleep

Sleep is a natural and most important process to improve overall health. Without this process, our body will not function properly. Read on to discover why do we sleep or what happens to our bodies when we don’t get enough sleep.

Just like we need food, air, and water for survival, we also need sleep. It is quite important to maintain good health. We sleep for about one-third of our lives.

During this process, major biological processes take place within our body, like the elimination of toxic wastes, cell repairing, restoration of energy, improved brain functioning, and release of certain hormones.

Why do we need sleep?

The exact purpose of sleep is still unknown. Scientists do not know why do we need sleep. But it is widely accepted this process is quite important for various biological processes.

It helps our bodies in different ways. Some of them are listed below.

Improves emotional health

When we sleep, the activity of the brain increases, especially in parts that control our emotions.

Enough sleep promotes the overall stability of the brain and improves certain parts of the brain that improves our emotional stability. These parts include the striatum, insula, amygdala, and hypo campus.

Various studies suggest that sleep and mental health is interlinked. If you do not get enough sleep, you may face mental health issues. Similarly, if you are suffering from any mental issue, it may also contribute to a lack of sleep.

When you get adequate sleep: your brain reacts to stressful events in a more adaptable manner.

Energy conservation theory of sleep 

Our metabolism slows down as we sleep. According to experts, our body needs sleep to conserve energy while reducing our calorie requirements.

It is said that 8 hours of sleep is enough to conserve almost 35% of our energy. According to the energy conservation theory of sleep, it makes our body conserve energy during times of the day when we are less efficient or when it is hard to search the food.

Restorative theory

According to the restorative theory of sleep, we need it for the restoration process of our body. It enables our bodies to repair and rejuvenate their cells, muscles, and tissues.

During this procedure, many essential hormones are produced. Some proteins are also synthesized.

Brain plasticity theory

According to this theory, sleep improves brain functioning by allowing the neurons and nerve cells to reorder. This reordering makes the brain clean up the toxic elements from the central nervous system. As a result, you feel fresh when you wake up in the morning after getting enough sleep.

This process also improves memory. It helps in converting short-term memories into the long-term. It also erases unnecessary information and helps in improving the learning ability of a person. Aside, it promotes problem-solving ability, creativity, concentration, and focus of a person.

Weight management

Ghrelin and leptin are hunger hormones. These hormones work to maintain and control weight. Ghrelin increases hunger while leptin suppresses it by increasing the feeling of fullness.

The sleeping process controls the production of these hormones and contributes to weight management. When you are sleeping, your body produces less ghrelin because you are not using enough amount of energy.

If you are not getting enough sleep, it may result in the production of more ghrelin. Increased levels of ghrelin may lead to increased calorie intake. Studies suggest that lack of sleep may lead to obesity and metabolic syndrome.

Protects against insulin resistance

Getting enough sleep may protect you from insulin resistance. Insulin is a hormone that makes efficient use of energy in your body.

If your body is resistant to insulin, it will not use the sugars efficiently. As a result, it may cause diabetes. When you get enough sleep, your cells remain healthy. They make use of glucose efficiently and regulate the blood glucose level.

Increase immunity

Lack of sleep can inhibit the ability of the body to fight off foreign invaders like bacteria and viruses. A healthy sleeping pattern strengthens the body’s immune system and protects it against numerous antigens.

It promotes the production of cytokines and antibodies. These proteins fight off inflammation and prevent developing various infections.

Heart health

Certain heart-related issues are associated with a lack of sleep. Some studies suggest its deprivation may contribute to various health issues, which may affect your heart.

It includes high blood pressure, insulin resistance, inflammation, and weight gain.

What happens when we sleep?

Our body goes through four stages during 7 to 9 hours of the sleeping cycle. This cycle repeats several times throughout the night. It can vary from 70 to 120 minutes. This pattern includes two main phases:

Non-rapid eye movement sleep (non-REM): It is the absence of eye movement.

Rapid eye movement sleep (REM): It is the stage at which the eyes move quickly.

During the four stages of the 7-8 hours of sleeping cycle, three phases of non-REM and one phase of REM sleep occurs.

Stage 1: During stage 1 of non-REM sleep, heart rate and eye movement slow down. It lasts usually for about 7 minutes.

Stage 2: During stage 2 of non-REM sleep, eye movement stops. The temperature of the body decreases, and muscles get relaxed. It is characterized by light sleep, and a person spends most of his time in stage 2 of non-REM sleep during the night.

Stage 3: Deep sleep begins during stage 3. It is the phase when all major biological processes start. From cell repairing to the restoration of energy – every process occurs in this phase. Stages 3 and 4 are critical for obtaining energy for the body and being active throughout the day after awakening.

Stage 4: This is a phase of deep sleep, just like stage 3. The heart rate increases and your eyes show rapid movement from side to side. The breathing process also speeds up during stage 4. REM sleep is also characterized by dreaming. This period is crucial for learning and memory since your brain processes all the information.

How much sleep do I need?

The average duration of sleep depends upon age. The recommended amount of sleep for people of different age groups is listed below.

How much sleep do I need

What happens when we do not get enough sleep?

Getting enough amount of sleep is crucial for maintaining proper health. It is important to get enough sleep to make our organs work properly. Insufficient sleep can affect our organs like the heart, lungs, brain, and kidneys.

Both children and adults require adequate sleep to function properly, both cognitively and physically.

Lack of sleep may result in the following consequences:

  • Mood swings
  • Low energy
  • Poor memory
  • Weight gain
  • Insulin resistance
  • Risk of diabetes
  • Insufficient learning ability
  • Poor concentration
  • Fatigue
  • Low immunity
  • High blood pressure
  • Increased risk of heart diseases


Sleep keeps our body healthy and energized that is the reason we do need sleep. It helps our body to restore and repair.

From proper brain functioning to the prevention of chronic health disorders, we need enough sleep according to our age. Lack of sleep may result in certain side effects like high BP, poor memory, weak immune system, and mood swings.

On average, an adult needs 7-9 hours of sleeping cycle. If you cannot sleep well, or face trouble while sleeping, talk to your doctor. A health care provider will help you identify the underlying cause of its deprivation and help you improve your cycles.

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