Sleep Cycles: Why They Affect Energy Levels

Article Summary:

• Sleep is vital for your overall health and well-being, but it’s not all equal. Your body goes through different stages during your sleep cycle, including REM sleep and non-REM sleep.
• The deep sleep stage is where most of your body’s recovery is thought to happen, including replenishing your energy stores.
• Getting good quality sleep is essential to fuel your energy levels and reduce stress, which both help with weight management.

Sleep Cycles: Why They Affect Energy Levels

Getting a good night’s sleep every night is one of the most important things you can do for your health. That’s because sleep is essential to give your body the time and fuel it needs to repair, recover and function at its best.

However, it’s not just about how much you sleep, but how well you sleep. In other words, your sleep quality. In this article we’ll help you understand the different sleep stages, how sleep affects your energy levels, and in turn how this can impact your health and weight loss goals.

What are the stages of sleep?

You might think that sleeping well is as simple as getting a full eight hours, but it’s important to understand the structure of your sleep too, also known as sleep architecture. While sleep duration is important, the type of sleep you’re getting is key to really reap its health benefits.

Sleep is an ultradian rhythm, meaning it’s a recurring biological cycle that lasts for less than 24 hours. Your sleep cycle is split into stages, where you’ll transition between REM (rapid eye movement) and non-REM (NREM) sleep. Each stage lasts an average of 90 minutes, and you’ll repeat this cycle around 4-6 times in one night. [1]

In total, there are 4 sleep stages, and each affects your body in different ways.

What are the stages of non-REM sleep?

There are 3 stages of NREM sleep, referred to as N1, N2 and N3.

• N1 is the lightest stage, where you gradually fall asleep. This usually only lasts a few minutes, but it’s easy to wake someone up during this stage.
• N2 is deeper, where your body starts to relax. Your body temperature starts to drop, muscles relax, and your heart and breathing slow. This takes up the majority of your sleep time.
• N3 is the deepest stage of sleep, also known as slow‑wave or delta wave sleep. This is the most restorative stage, where your body does most of its recovery and repair work and supports immune function. It’s harder to wake someone up from this stage, and it’s the most important for feeling energized and refreshed the next day.

What happens during REM sleep?

The fourth stage of sleep is REM or rapid eye movement sleep, named because of the eye movements that it causes. Some refer to it as your ‘dream’ sleep, as it’s when your most vivid dreams happen. During REM sleep, brain activity increases to process emotions and memories, so your eyes move rapidly, breathing becomes irregular, heart rate and blood pressure rise, and voluntary muscles may be temporarily paralyzed.

What affects your sleep cycle?

Your sleep cycle is regulated by your body's internal clock, also known as the circadian rhythm. All kinds of factors can affect your sleep cycle, including:

Light exposure

This is the strongest cue for your internal clock, which is why it's so important to get plenty of natural light during the day. Artificial light can suppress melatonin production, which makes it harder to fall asleep.

Lifestyle and diet

Just as the foods you eat affect your overall health, they can impact your sleep too. Having alcohol or caffeine late in the day, or doing intensive exercise close to bedtime can interfere with getting a good night's rest. Your schedule can impact it too, with shift work and jet lag affecting your sleep-wake cycle. [2]

Age and genetics

Whether you're an early bird or a night owl is thought to be largely determined by genetics, and how fast or slow your internal clock ticks. Your sleep also changes as you age, sometimes becoming more difficult to drift off or less time in deep sleep. [3] [4]

Stress

It won't be a surprise that stress can impact your sleep, causing you to toss and turn. Mental health conditions like anxiety and depression can also cause sleep disruption.

Environment

Sometimes referred to as your 'sleep hygiene', optimizing your environment for better sleep is even more important in the digital age. Light and noise from digital devices can disrupt your sleep, while hot temperatures and even changing where you sleep to somewhere that’s unfamiliar (such as staying in a hotel) can have an impact on sleep quality.

Sleep disorders

Your health impacts your sleep, too. Disorders like sleep apnea, a potentially serious condition where your breathing stops and starts repeatedly during sleep, disrupt your rest and should be treated to avoid long-term health risks. [5] Restless legs syndrome (RLS) can also interrupt your sleep cycle, causing an urge to constantly move the legs. [6] If you’re struggling with sleep disorders, it’s important to talk to a clinician or doctor to get the right diagnosis and the help you need.

How sleep affects your energy levels

Now that you know the stages of your sleep cycle, you can think of deep or slow-wave sleep as your body’s way of recharging its batteries. This restoration stage is where your body replenishes its cellular energy (called ATP). If it's cut short or interrupted, you'll wake up feeling groggy and will have less physical energy, even if your sleep duration wasn't impacted. [7]

Your internal body clock is also important for how alert or sleepy you feel. So when your sleep-wake timing is irregular, for example due to shift work, late nights or jet lag, this clock can go out of sync. And that leaves you feeling sleepy when you need to be awake, or more wired when you want to fall asleep.

Why sleep is important for weight management

Whether you’re looking to maintain a healthy weight or have specific weight loss goals, getting sufficient and quality sleep needs to be part of your plan.

Hormone production

Studies have shown that there is a direct link between sleep deprivation and obesity. [8] There are many reasons for this, with one being the way sleep affects hormone production, especially ghrelin and leptin.

These appetite-regulating hormones tell your body when you’re hungry (ghrelin) and when you’re full (leptin). When you don’t get enough sleep, ghrelin increases and leptin decreases, leading to more hunger pangs and cravings. [9] This means you might eat at least 300 calories more the day after a bad night’s sleep, making maintaining a healthy weight or keeping your weight loss goals on track much harder. [10]

Your stress hormone, cortisol, also increases when you don’t sleep well. This can impact your weight, too, because cortisol encourages the body to conserve energy and store more as fat, especially around the abdomen. [8]

Metabolism

Sleep also impacts your metabolism, which is the process your body uses to convert food into energy. Not getting enough sleep can affect how your body metabolizes glucose, causing fatigue, hunger and food cravings. If the sleep deprivation continues, this can cause long-term issues by impacting how your body responds to insulin, the hormone that regulates your blood sugar. Known as insulin resistance, this can lead to weight gain and type 2 diabetes. [11]

Exercise and nutrition

If your batteries are running low after a poor night’s sleep, you’ll struggle to find the energy to exercise. Movement is an essential part of any weight loss plan, but low energy means you might skip a workout or put in less effort, so you burn fewer calories.

When you’re tired you're also more likely to make poor food choices, opting for convenience foods, takeaways and snacks rather than cooking and planning your own meals.

Fat loss vs lean tissue

If you're trying to lose weight, sleep can affect your body composition too. In one controlled study, when people cut their sleep to just 5.5 hours while dieting, the proportion of weight lost from fat dropped by more than half. Instead, more of the loss came from lean mass. When they had enough sleep, more than half of the weight they lost was from fat. [12]

How to improve your sleep cycle for a healthier weight

So how much sleep do you need? For most adults, getting 7-9 hours of sleep consistently alongside a regular sleep-wake schedule should be sufficient. This will support more stable energy levels, leading to better food choices and more effective exercise to help keep your weight loss goals on track.

Here are a few tips to help you improve your sleep schedule and overall sleep quality:

• Get plenty of daylight, especially during your first hour after waking.
• Aim to wake up and go to sleep at around the same time every day, including weekends.
• Avoid alcohol, caffeine and heavy meals in the 2-3 hours before bed.
• Do more intense exercise earlier in the day, and gentle exercise such as yoga in the evening.
• Reduce noise and light disruptions in your bedroom, and have a wind down routine with less screen time in the hours before you go to sleep.

Find out more about weight loss support with MedExpress.

References

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