Circadian Rhythm: Why It Matters When You Sleep, Eat, and Exercise?

In our efforts to have more energy and live a long, fulfilling life, we often overlook one of the most fundamental biological principles: the human body operates according to its natural internal clock. And if we fail to follow it, chaos sets in – our metabolic health, recovery, and physical and mental performance all fall out of sync. So how can we get on the same page as our circadian rhythm?

What is the circadian rhythm?

The circadian rhythm is an approximately 24-hour biological cycle that regulates most of the body’s essential processes – sleep, wakefulness, hormone production, body temperature, digestion, and metabolism.

Its main “conductor” is the suprachiasmatic nucleus (SCN). This group of neurons, located in the hypothalamus, continuously receives information about the intensity and color of light from the retina and uses it to synchronize the rest of the body.

Today, we also know that the brain is not the only organ with its own biological clock. These clocks are found in virtually all tissues and organs – in the muscles, liver, adipose tissue, and intestines. And for the body to function optimally, all these “clockworks” need to be aligned.

Why should we care about the circadian rhythm?

From an evolutionary perspective, we spent millions of years adapting to the alternation of day and night. Only in the last few decades have we begun spending our evenings under artificial lighting, working shifts, or falling asleep with a phone in our hand. And it has not exactly paid off.

Research shows that long-term disruption of the circadian rhythm is associated with a higher risk of:

• metabolic disorders,

• obesity,

• insulin resistance,

• cardiovascular disease,

• mood disorders,

• poorer recovery and sleep quality.

That is why, when it comes to sleep, we no longer emphasize only its duration, but also its quality and timing. The same applies to food, movement, and light exposure, where when and what kind of light we are exposed to every day is crucial.

How can you tell if your circadian rhythm is “out of sync”?

Occasional fatigue after a demanding week is normal. But if, over the long term, you:

• wake up tired in the morning even after getting enough sleep,

• cannot fall asleep in the evening even though you are exhausted during the day,

• experience significant energy crashes throughout the day,

• struggle with ravenous hunger late in the evening,

the problem may lie in a disrupted circadian rhythm.

Groups that are “objectively” at risk include people who frequently travel across time zones or work shifts, as well as parents of young children. However, we can easily throw our internal clocks off balance simply through a hectic lifestyle or a lack of awareness of the most common factors that negatively affect the circadian rhythm.

How can you synchronize your biological clock?

In everyday life, we usually cannot influence absolutely everything, so we rarely achieve perfectly ideal conditions. However, a few basic and relatively small changes are often enough to bring about a significant improvement.

1. Start your day with light

The strongest regulator of the circadian rhythm is light. Shortly after waking up – ideally within the first waking hour – go outside for 5 to 10 minutes, or at least open a window and let your eyes have contact with natural daylight. Even an overcast sky will serve you many times better than ordinary indoor lighting.

Morning light exposure helps suppress residual production of the so-called sleep hormone melatonin and kick-start wakefulness. At the same time, it synchronizes the biological clock and influences the proper timing of evening tiredness. In other words, how well you sleep in the evening is already being determined in the morning.

2. Dim the lights in the evening

Light therefore works a little like a start button – one we do not want to keep pressing in the evening. Yet we do it all the time, and we even call it relaxation. A common bad habit that lowers our sleep quality is endless scrolling on a phone or watching films in the evening. Screens and LED lighting emit light with a blue component, which signals to the brain that it should stay alert.

For evening lighting, replace harsh white light with warmer light sources and, two to three hours before bedtime, limit work on your computer and phone. Try swapping these activities for a book, or at least use night modes on your screens or special red glasses that filter out part of the blue light.

3. Go to bed at roughly the same time

The biological clock has its own timetable – and the body is usually happiest when it does not have to rewrite it every day. So if you want to do it a favor, it comes down to one thing: regularity. Studies also confirm its benefits: irregular sleep is associated with poorer health outcomes independently of sleep duration itself.

Of course, you do not have to fall asleep every day at exactly 10:03 p.m., but if you sometimes go to bed early in the evening and other times at one in the morning, the body has a hard time finding its bearings. Nor is catching up on sleep during the weekend the most suitable strategy.

4. Eat during the day, not at night

Food is also an important timing signal. When we eat, processing food becomes the body’s absolute priority and less essential bodily functions are temporarily pushed into the background. A large meal late in the evening can therefore disrupt nighttime regenerative processes.

In addition, metabolism is not equally efficient throughout the day – insulin sensitivity tends to be higher in the morning and before noon, so the body handles even a larger load of carbohydrates more easily and processes them more effectively. In the evening, this ability naturally decreases.

In practice, this means:

• try to consume most of your calories during the day,

• do not eat right before bedtime,

• limit nighttime snacking,

• give your body a longer overnight break without food.

If you extend your nighttime “fasting window” even further, you can benefit from so-called intermittent fasting , which makes it easier for the body to carry out its natural cellular renewal.

► Read more in our article on autophagy.

5. Move at the right time

Although getting enough physical activity is important for high-quality sleep, intense evening training can make falling asleep more difficult for many of us.

So if you find yourself tossing and turning in bed after exercising in the evening, try moving more demanding workouts to an earlier part of the day. If you need or feel like moving in the evening, choose a walk or a calm yoga class instead.

6. Do not overdo it with caffeine

Caffeine blocks receptors for adenosine – a substance that accumulates during the day, calms the nervous system, and creates a feeling of tiredness. Caffeine remains active in the body for roughly 5 to 7 hours, and even longer in more sensitive individuals. Coffee can therefore negatively affect falling asleep even when it seems you drank it long ago – for example, during an afternoon break.

For better sleep, try cutting out caffeine at least 8 hours before your planned bedtime. But beware – besides coffee, it is also found in tea, energy drinks, and cola beverages.

How is the circadian rhythm connected to longevity?

When people hear the word longevity, most imagine expensive tests, complicated protocols, or the latest biohacking trends. In reality, however, something much simpler may have a greater impact – a regular routine.

Aligning with our biological clock is one of the essential prerequisites for high-quality sleep, during which a number of processes take place related to tissue repair, immune system regulation, hormonal balance, and cellular maintenance.

Disruption of the biological clock also affects processes related to inflammation, metabolism, and cellular aging. That is why understanding and respecting the circadian rhythm is now considered one of the fundamental pillars of long-term health.

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Did you know…

…that getting enough of certain nutrients also contributes to sleep quality?

For recovery and the proper functioning of the nervous system, the following are important, for example:

• Magnesium – helps reduce both mental and muscular tension.
• L-theanine (an amino acid naturally found in green tea) – is often associated with a sense of relaxation without excessive dullness.
• Lemon balm, chamomile, and other botanical extracts – have been used for generations to support relaxation.

Highly absorbable magnesium, L-theanine, and carefully selected herbal extracts can also be found in DeepRest, designed for calmer evenings and deeper nighttime recovery. For more energy during the day, consider synergistic revitalizing supplements instead of caffeine stimulants, such as LifeCharge, which may provide much more stable results.

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What should you take away from this?

Regular sleep, plenty of morning light, reducing light in the evening, sensible meal timing, and daily movement are among the best-researched ways to align the biological clock with how our body is designed to function.

And that is often where the real potential for long-term health lies – not in extremes, but in consistent habits that we can maintain for years.

Sources:

• https://pubmed.ncbi.nlm.nih.gov/31768006/
• https://pmc.ncbi.nlm.nih.gov/articles/PMC5449130/
• https://pmc.ncbi.nlm.nih.gov/articles/PMC5995632/
• https://www.nature.com/articles/s44271-024-00159-5
• https://pubmed.ncbi.nlm.nih.gov/31938759/
• https://pmc.ncbi.nlm.nih.gov/articles/PMC5272178/