Do you ever wake up with grogginess you can’t seem to shake, struggle to keep your eyes open come 3 p.m., or simply feel slow mentally and physically day after day? Even worse, do you always feel tired, even when you get eight hours of sleep and have just sunk a double-shot espresso?
Having more energy makes everything in life easier and more enjoyable, but too many of us go through life without it. Below, we’ll cover the reasons you might be feeling tired all the time, and why sleep debt and circadian misalignment are most likely to blame.
Let’s kick off by saying there are many reasons you might be feeling tired all the time, and some of these are underlying health problems. So, of course, if chronic fatigue is impacting your quality of life, speak to healthcare professionals to rule out anything serious.
Common causes of fatigue include:
However, most of the time, a lack of energy is caused by two main things:
Sleep debt and circadian rhythm come together to form the two laws of sleep, and they’re the biggest things affecting your energy levels each day.
Get these things right and you’ll not only boost how much energy you have each day, you’ll know exactly how to harness it to get the most from it. Get them wrong, however, and you’ll be left dragging your feet, battling brain fog, and lacking motivation to do anything — and that’s not even mentioning the many negative health impacts.
Let’s dive into these two important things and how exactly they could be the reasons you’re always feeling tired.
Sleep debt is the running total of how much sleep you owe your body over the last 14 nights. It’s measured against your sleep need, which is the genetically determined amount of sleep you need.
While the common advice is to get eight hours of shut-eye a night, that ideal amount of sleep is different for each of us. The average sleep need is 8 hours 10 minutes, plus or minus 44 minutes or so, but 13.5% of the population may need 9 hours or more sleep a night.
It’s hard to figure out your sleep need alone, though. Morning grogginess (also called sleep inertia) is normal, but it makes you feel like you haven’t had enough sleep, even when you have. On the other hand, a strong coffee or two can give you a temporary energy boost even if you haven't met your sleep need.
Plus, it’s sometimes hard to notice when you’re sleep deprived as we adapt to sleep loss over time. We might feel like we’re doing fine, when actually our performance, health, and energy potential are all below what they could be.
The RISE app removes all this uncertainty and uses your phone use behavior and proprietary sleep-science-based models to work out your sleep need. You’ll then get an amount of sleep to aim for each night.
Once you know your sleep need, you may realize you haven’t been getting this. In this case, you’ll have built up sleep debt. And how much sleep you’ve missed out on will determine how much sleep debt you’re carrying, and how much energy you’re feeling.
RISE works out your sleep debt and keeps track of it each night. We recommend keeping it below five hours to maximize your energy levels. Got a high amount of sleep debt? That’s the most likely culprit for what’s sabotaging your energy levels each day.
Heads-up: The jury’s still out on whether you can pay back chronic sleep debt, or sleep debt that’s built up over years. But studies show it is possible to recover from acute sleep debt, the kind you’ve built up over the last two weeks. More on how to do this soon.
It’s not enough to just keep your sleep debt low, to feel maximum energy each day, you need to be in circadian alignment.
Circadian alignment simply means your social clock (the times you do things like sleep and wake up, eat, and exercise each day based on your life commitments, like work and kids) aligns with your biological clock. Your biological clock is your circadian rhythm. It runs on a roughly 24-hour cycle and dictates your energy levels throughout the day as well as things like hunger levels, body temperature, and hormone secretion.
Your energy levels fluctuate naturally, even when you’re high in energy overall. The pattern goes like this:
If you’re not in circadian alignment, your body will produce melatonin and cortisol — some of the primary hormones responsible for how awake you feel — at the wrong times for your daily schedule.
You might be out of sync with your circadian rhythm if:
However, there’s more than just one internal body clock to think about. There’s the master clock in your brain that controls your sleep-wake cycle — this is called the suprachiasmatic nucleus (SCN). There’s also a whole network of body clocks present in almost every tissue and organ in your body.
Everything from your gut to your liver, your metabolism to your immune system runs on its own circadian rhythm. These are called your peripheral clocks, and they can get out of sync, too. For example, if you eat at odd or irregular times, you can upset your digestive clock, leading to circadian misalignment.
Circadian misalignment doesn’t just lead to low energy, though. It impacts your overall wellness as it increases your risk of weight gain, disrupted glucose metabolism, diabetes, heart disease, cancer, and mood disorders — just to name a few.
And you’ll not only feel sleepy, your attention, cognitive function, and visual-motor performance will also take a hit.
Sleep debt and circadian rhythm work independently from each other, but also interrelatedly.
The more sleep debt you have, the more you’ll feel the energy dips of your circadian rhythm and those energy peaks will be smaller. And the more out of alignment you are with your circadian rhythm, the harder it is to meet your sleep need — as you won’t feel sleepy at the right times each night — meaning you’ll build up sleep debt. It’s a vicious cycle, leading to low energy day after day.
If you don’t get enough sleep, you’re obviously going to wake up and immediately want to hit the snooze button the next day. But you can also meet your sleep need, be in circadian alignment, and still wake up feeling tired.
This comes down to sleep inertia. Every moment you're awake, a natural compound called adenosine builds up in your brain. When it reaches a certain level, you’ll feel drowsy and get the urge to sleep — also known as sleep pressure.
When you do sleep, adenosine is purged from your system. The balance is reset and the cycle begins again when you wake up. This is all part of the homeostatic process — or the balance between sleep and wakefulness.
When you don’t get enough sleep, however, your body doesn’t have enough time to purge all the adenosine in your brain. You wake up with it still in your system, making you feel much groggier than usual.
But even if you have had enough sleep, there’s still trace amounts of adenosine in your system, leaving you with that groggy feeling. Give it 60 to 90 minutes though, and you should start feeling your energy levels rise. This grogginess will feel worse if you’ve got high sleep debt, but it’ll still be there even if you don’t (though you’ll feel groggier than usual if you met your sleep need last night, but still have sleep debt from the last week or so).
The RISE app predicts how long your grogginess will last each morning, so you can plan your day with it in mind. We cover ways to manage sleep inertia here.
You may not have as much energy as you like throughout the day, but if it really hits you in the afternoon, you can blame your circadian rhythm for that and the natural dip in energy that comes in the afternoon.
This afternoon dip has been linked with sleepiness, lower productivity, more car accidents, and even our ethics take a hit.
When your sleep debt is low, this dip in energy will be less noticeable. If you’re carrying a lot of sleep debt, however, you’ll feel your energy levels plummet in the afternoon even more than usual.
You can use the RISE app to see when this dip in energy is coming up, so you can schedule your tasks around this.
We’ve covered how to stay productive through your afternoon dip here.
Feel like you’re meeting your sleep need each night, but still lacking in energy each day? It could be morning grogginess and circadian misalignment, but here are three other culprits:
Learn more about what gives you energy here.
We’ve covered how to get more energy in detail here. But here are the two main things you can focus on that will make a real difference to your energy levels.
First, find out what your individual sleep need is. Then start meeting it each night. That, of course, is easier said than done. But you can use sleep hygiene — the set of daily behaviors that help you sleep each night — to do it. We cover more about sleep hygiene here.
Meeting your sleep need going forward will help boost your energy levels, but you’ll also feel the effects of the lack of sleep you’ve had recently. Use RISE to work out your sleep debt. If you’re carrying more than five hours of it, this may well be the reason you’re feeling tired.
You can catch up on sleep by:
As well as paying down your sleep debt, you need to think about your circadian rhythm and getting back in sync if your daily life doesn’t match it.
The easiest way to stay in sync with your body clock is to keep a consistent sleep schedule, even on weekends. Check RISE to see when your body naturally wants to wake up — we call this your “Wake Zone” — and when it wants to go to sleep.
You’ll see your Melatonin Window each evening, which is the ideal time to go to bed. During this one-hour window, your rate of melatonin production (the sleep hormone) will be at its highest, so you’ll find it easier to fall and stay asleep now than if you went to sleep at any other time.
RISE users on iOS 1.202 and above can click here to set up their Melatonin Window reminder.
Bonus tip: If the best times to go to sleep and wake up for you don’t fit with your day-to-day life — perhaps you’re a night owl who needs to get up early for work — you can shift your circadian rhythm to a schedule where you can be in sync with it each day. You can learn how to reset your circadian rhythm here.
Time your meals, exercise, and light exposure to your circadian rhythm, too. All three of these things are zeitgebers (German and science-speak for time-givers), or cues that can change the timing of your circadian rhythm.
Get bright light in the morning and throughout the day, and avoid large meals, exercise, and bright light exposure in the wind-down period before bed, and eat at roughly the same times each day. Check RISE for when to avoid these things based on your circadian rhythm each day.
RISE users on iOS 1.202 and above can click here to set up personalized reminders to get bright light in the morning, avoid late meals, exercise, and light exposure.
Syncing up with your circadian rhythm also extends to what you do during the day and how you spend your energy when you have it.
You can schedule your day to fit your natural peaks and dips in energy. Schedule more challenging tasks for your peaks — think writing a report, giving a presentation, or solving a programming problem — and easier tasks for your energy dips — like admin, emails, or even taking a nap.
By scheduling your day to match your energy levels, you’ll be maximizing those times when your energy is higher, and working with — instead of fighting against — those natural dips in energy.
RISE users on iOS 1.202 and above can click here to get reminders for when their peaks and dips are coming up.
Heads-up: If you try these things and you’re still feeling tired all the time, speak to a doctor to check for a health condition or sleep problem that could be causing this. They may do blood tests, suggest dietary supplements, or recommend lifestyle changes like increasing your physical activity or eating a more balanced diet.
That was a lot of science, so let’s sum up. You may be feeling tired because of an underlying cause like a medical condition or nutritional deficiency, but sleep debt and circadian misalignment are also common reasons for lingering tiredness — and those two things can be fixed with lifestyle tweaks.
The RISE app can help. The app works out your individual sleep need — so no more second-guessing if you’ve had enough sleep or not. It then works out how much sleep debt you have and keeps track as you pay it back. You can see a prediction of your circadian rhythm each day, helping you schedule your sleep-wake cycle and daily tasks with it, and get reminders for sleep hygiene habits to do each day, to help you get a good night’s sleep each night. Head here for a deeper dive on how to get more energy with the RISE personal energy tracker app.
With low sleep debt and circadian alignment, you’ll be well on your way to boosting your energy levels and seeing what you can accomplish when you don’t feel tired all the time.
If you’re female and always feel tired, it could be due to your period, pregnancy, menopause, an underlying condition, or nutritional deficiency. Sleep debt and circadian misalignment are also common culprits.
Yes, fatigue is a common symptom of COVID. Fatigue may only last a few days while you’re battling the virus, but it is also a symptom of long COVID and can linger for weeks after the initial illness.
If you’ve tried reducing fatigue by paying down sleep debt and getting in circadian alignment and you’re still feeling tired after a week or two, speak to a doctor to rule out medical conditions or sleep disorders.
To get your energy back, work on meeting your sleep need each night with good sleep hygiene, paying down sleep debt by taking naps or going to bed a little earlier, and getting in circadian alignment with a solid sleep schedule that matches your chronotype.
Learn more about Rise for sales teams.
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