The Importance of Sleep and How to Get Better Sleep

Written By MARTIN KHOO

5 Reasons why sleep is so critical to fitness and 5 ways to maximise your sleep efficiency.

As a personal trainer, clients fully expect me to highlight the importance of exercise and nutrition for optimal health, fitness and well-being; but I believe sleep should be assigned equal footing. Sleep has a massive impact on our physiology, it makes performing optimal eating and training easier, and allows to get more out of our training and nutrition after the event.

The evidence is clear, we are designed by evolution to sleep for a third of our lives, and its critical for our health. The aim of this article is to provide the “why” to help understand its importance and the “how” to help us maximise the health benefits of sleep. So in this article I’m going to outline five physiological reasons to why it improves health and fitness, and 5 steps we can take to improve our sleep.

The Highlights

What A Good Nights Sleep Does For The Body

The Science

1. Optimal Sleep Increases Fat Burning

During sleep, your body switches its primary fuel source from glucose (sugar) to lipids (fats). So quality sleep can significantly increase fat metabolism.

This happens because you are in a fasted state. Since you aren't eating for 7–9 hours, your insulin levels drop, signalling your body to unlock stored fat to fuel essential maintenance tasks like cell repair, muscle energy replenishment, breathing, and brain function.

For those who like a bit more science the following are the specific hormonal cocktail at night our body uses to metabolise fat.

  • Human Growth Hormone (HGH): This is the heavy lifter. During deep sleep (specifically Stage 3 non-REM), your pituitary gland releases pulses of HGH. This hormone stimulates lipolysis—the breakdown of fat cells into fatty acids to be used as energy—while simultaneously preserving muscle mass.

  • Insulin (The Switch): Fat burning can only occur when insulin is low. When you sleep, insulin levels naturally drop (assuming you haven't eaten recently). This "opens the gates" for fat stores to be released.

  • Cortisol: Levels of this stress hormone naturally rise toward the morning (around 4–6 AM) to wake you up. This spike helps mobilize energy stores (fat and sugar) to get you moving.

2. Optimal Sleep Improves Muscle Health & Hypertrophy

When you exercise, you create microscopic tears in your muscle fibres. Sleep provides the optimal environment for these fibres to heal and rebuild, making them stronger and larger—a process known as muscle hypertrophy, and this is what we want to achieve at our personal training studio. There are 4 main mechanisms in which sleep aids muscle gain.

  • Protein Synthesis: While you sleep, especially if you consumed protein before bed, your body continues the process of protein synthesis—the creation of new muscle tissue. This process is essential for muscle growth and recovering from muscle damage.

  • Human Growth Hormone (HGH) Release: The most crucial element is the release of Human Growth Hormone (HGH). Your pituitary gland secretes the majority of your daily HGH during deep sleep (Slow-Wave Sleep). HGH is an anabolic (muscle-building) hormone that: Promotes Tissue Repair and Drives Protein Synthesis.

  • Energy Restoration: Your muscles use a significant amount of stored energy, called glycogen, during exercise. Sleep is the primary time your body fully reloads these fuel tanks by replenishing glycogen stores, mostly via the liver. Poor sleep has been found significantly reduce next day endurance performance.

  • Hormonal Balance (Anti-Catabolism): Sleep helps regulate the hormones that determine whether your body is in a state of building muscle (anabolic) or breaking it down (catabolic). One of the key hormones that will rise during sleep is testosterone (anabolic) and one that will lower is cortisol (catabolic).

3. Optimal Sleep Upregulates Immune System

You might assume your immune system "powers down" when you sleep, but the opposite is true. While your conscious brain, digestive system, and muscles rest, your immune system actually ramps up its activity, using sleep as a strategic window to perform its most heavy-duty work.

This happens because your body isn't spending energy on moving or thinking, allowing it to divert resources to defence. Here is how sleep directly impacts your immune function.

  • The "Sticky" T-Cell Phenomenon- T-cells are your body's elite "hunter-killer" cells—they identify pathogens (like flu viruses) and destroy them. However, to kill a virus-infected cell, a T-cell must first attach or "stick" to it. When you sleep you experience lower levels of stress hormones (adrenaline, noradrenaline) and prostaglandins. These chemical messengers allows the integrins to become active and "sticky" again, making them more lethal and efficient at latching onto and destroying viruses while you sleep.

  • Cytokine Production (The Alarm System)- Cytokines are small proteins that act as the messengers of the immune system. They coordinate the body's response to infection and inflammation. During sleep, your immune system releases pro-inflammatory cytokines (like Interleukin-1). This is the process process that kills pathogens.

  • Immunological Memory- Sleep also helps your immune system "remember" invaders. During deep sleep, there is a complex interaction between Antigen-Presenting Cells (APCs) and T-Helper cells. The APCs effectively "upload" data about recent viruses to the T-cells. This process moves the information into "long-term immunological memory." Without sleep, your body struggles to retain the blueprint for how to fight a specific virus in the future.

4. Optimal Sleep Cleanses Brain

  • The Glymphatic System (Waste Clearance): This is the most direct form of brain repair, often likened to the brain's unique "plumbing system." When you enter deep sleep (Slow-Wave Sleep), your brain's glial cells cause the brain cells to shrink by up to 60%. This shrinking opens up the spaces between the neurons. This opened space allows cerebrospinal fluid (CSF) to flow rapidly through the brain tissue, sweeping away metabolic waste products that built up during the day's activity. This process is crucial for removing neurotoxic proteins like beta-amyloid and tau. The build-up of these proteins is strongly implicated in neurodegenerative diseases like Alzheimer's.

  • Synaptic Downscaling (Energy Reset): During the day, every experience, thought, and sensation strengthens connections (synapses) between neurons. This is how we learn. However, these connections use a lot of energy and can become unsustainable. During Non-REM sleep, the brain actively prunes and weakens the non-essential or less-used synaptic connections. By weakening these less-important connections, the brain reduces its overall energy consumption. this ensures that the next day, the truly important memories and pathways are loud and clear, while conserving metabolic resources. 

5. Optimal Sleep Syncs Our 24 Hour Body Clock

The term diurnal rhythm generally refers to any biological cycle that operates on a 24-hour schedule and is aligned with the day/night cycle (like body temperature, alertness, and hormone levels). The most important of these rhythms is the circadian rhythm, which is the master clock of the human body.

Sleep is not just governed by the diurnal (circadian) rhythm; the act of sleeping properly is what allows the rhythm to effectively regulate all other body systems.

By clearing the sleep pressure every night, sleep restores the homeostatic balance, allowing the Suprachiasmatic Nucleus (SCN) which resides in our brain (your master clock) to take over and dictate the next 16 hours of optimal wakefulness. Without a full reset from sleep, your sense of daytime alertness is compromised.

  • Hormonal Reset and Anchoring: Sleep allows for the precise, scheduled release and suppression of key hormones, which anchors your rhythm to the 24-hour clock. like Melatonin (The Sleep Signal) and Cortisol (The Wake Signal). Melatonin signals to the entire body that it is biological night. Cortisol levels naturally rise toward the end of your sleep cycle (around 4-6 AM) to help you wake up with energy and alertness. Consistent and quality sleep time allow for these hormones to align allowing for tiredness in the evening and alertness in the morning.

  • Adenosine Clearance (Homeostatic Balance): When you are awake, a chemical called adenosine builds up in the brain. This creates "sleep pressure"—the longer you are awake, the sleepier you get. The primary function of sleep is to clear this adenosine. By clearing the sleep pressure every night, sleep restores the homeostatic balance, allowing the Suprachiasmatic Nucleus (SCN) (your master clock) to take over and dictate the next 16 hours of optimal wakefulness. Without a full reset from sleep, your sense of daytime alertness is compromised.

  • Synchronizing "Peripheral Clocks": While the SCN in your brain is the master clock, almost every organ in your body has its own peripheral clock (in the liver, heart, muscles, etc.). These peripheral clocks control processes like metabolism, blood pressure, and digestion.The signals from the SCN need a consistent, scheduled sleep-wake cycle to reliably synchronize these hundreds of peripheral clocks across the body. When you get inconsistent sleep (e.g., sleeping in late on weekends or jet lag), these peripheral clocks fall out of sync with the master clock. This circadian misalignment is why disrupted sleep immediately leads to issues with hunger hormones, digestion, and glucose regulation.

How to Get A Better Nights Sleep

Eating Before Bed

I strongly recommend that my clients try to stop eating three hours before bed. I appreciate that his isn’t always possible but its important to have an optimal goal to aim for. But the evidence is clear, if your body is digesting food while you sleep, it will lower the quality of your sleep and interrupt vital physiological processes we outlined above.

Drinking Before Bed

Avoid drinking 2 hours before bed. The sensation of needing to urinate is often cited as the number one reason of waking from sleep (along with pets who sleep in the bed). From personal experience it just takes a couple of sips for me to close to bed to wake up needing to go to the toilet. Avoiding drinking fluids 2 hours before bed and you will significantly improve depth, duration, and quality of your sleep.

Screen Time Before Bed

Its definitely the hard one for people in my experience, but try and avoid screens for 1 hour before bed. Blue light from a screen will trick your brain into thinking its day time and muddle up your 24 hour body clock. A good habit swap is reading a book before bed rather than looking at your phone.

Caffeine Before Bed

I once read there are three different types of people, according to their genetic make up, with each responding to caffeine in three different ways. Those who shouldn’t drink coffee at all, those who do well on 1-2 cups a day and those who can drink as much as they want. Regardless of the category you fall into, I would recommend not to drinking coffee after 3pm to enhance sleep quality. This is due to caffeine molecules blocking adenosine molecules at the brain receptors, which are critical for the feeling of tiredness we experience when we need to sleep, and slowing down nerve activity.

Consistent Bedtime Routine

I recently came across some interesting research by a neuro-scientist who found that military and elite athletes performed better when they maintained a consistent sleep/ waking time pattern, meaning they fell asleep and woke up at the same time every day. Its suggested that this enhances and syncs our 24 body clock allowing for better quality of sleep and faster rates of falling asleep.

Alcohol

Here’s a bonus one, drinking alcohol before bed reduces the quality of our sleep. It may help you fall asleep, but evidence has shown that it reduces certain brainwave patterns associated with deep sleep needed for optimal brain health. I would avoid drinking before bed when possible and using it as a sleep aid.


Conclusion

I hope the following article has given you some motivation for a good nights sleep and some practical tips on how to improve the quality of your sleep. So have an early night tonight and wake up fresh tomorrow, sweat dreams!

MARTIN KHOO
Next

Breakfast- What to eat