How circadian rhythm impacts health

We sleep, eat, concentrate, and move according to an "internal clock," a biological cycle that regulates most of our body's processes: the circadian rhythm.

Plate with three dishes representing the different meals of the day.

This approximately 24-hour cycle marks the timing of sleep, body temperature, hormone secretion, and energy metabolism. When we respect it, our body functions in harmony. But when we disrupt it, imbalances occur that directly affect physical, mental, and emotional health.

In this article, we explore what the circadian rhythm is, why it's so important for your well-being, and how you can take care of it with simple habits.

What is the circadian rhythm?

The circadian rhythm is regulated by the suprachiasmatic nucleus (SCN), a structure in the brain that functions as a central pacemaker. This internal clock receives information about light and darkness and synchronizes biological clocks throughout the body.

Although we usually associate it with sleeping at night and being awake during the day, the circadian rhythm is much more complex. All organs and tissues have their own biological clocks that determine, for example:

  • When it is most efficient to digest food.
  • At what times of day the body is ready to repair tissues.
  • When the immune system is most strongly activated.

This field of study is known as chronobiology, and it has shown that living in tune with our internal rhythms is key to lasting health.

How does the circadian rhythm affect health?

Respecting our biological clock helps maintain internal balance. However, factors such as night shift work, jet lag, excessive exposure to screens at night, or a lack of stable routines can lead to circadian disruption.

Various scientific studies have shown that this disruption is associated with multiple health problems:

Poor quality sleep

Circadian rhythm disruption causes insomnia, nighttime awakenings, and daytime sleepiness. According to Czeisler & Gooley (2007, Nature), constant disruptions to the sleep-wake rhythm reduce the quality of rest and impair cognitive performance.

Metabolic disorders

A mismatch between eating schedules and internal rhythms increases the risk of obesity, insulin resistance, and type 2 diabetes. Scheer et al. (2009, PNAS) demonstrated that eating outside of the proper circadian timing alters glucose tolerance and promotes weight gain.

Cardiovascular health

The circadian clock regulates blood pressure and heart rate. Takeda & Maemura (2011, Nature Reviews Cardiology) showed that people with chronic circadian disruptions have a higher incidence of hypertension and heart attacks.

Emotional well-being

Poor sleep and living against one's internal clock are linked to depression, anxiety, and increased vulnerability to stress. Walker et al. (2020, Nature Reviews Neuroscience) highlight the relationship between chronodisruption and mental health.

Starry night with a crescent moon and plants at night.

Circadian rhythm and nutrition

Nutrition also follows circadian patterns. Eating at odd hours, skipping meals, or eating dinner late can disrupt metabolism.

  • Breakfast: activates metabolism and provides energy.
  • Lunch and dinner: optimal times for the highest calorie intake.
  • Light dinner: promotes rest and digestion.

In addition, the type of food influences:

  • Fruits, vegetables, and fiber help regulate metabolism.
  • Caffeine in the afternoon or evening interferes with melatonin.
  • Alcohol alters sleep phases and disrupts rhythms.

Habits to Take Care of Your Biological Clock

The good news is that we can align our circadian rhythms with our environment through healthy routines:

  • Exposure to natural light: Go for a walk in the morning or open the windows to regulate melatonin secretion and increase energy.
  • Maintain regular schedules: Go to bed and wake up at the same time every day, even on weekends.
  • Reduce screen time before bed: Blue light inhibits melatonin. Turn off devices 1–2 hours before bedtime or use night filters.
  • Adjust your diet: Eat a light dinner and avoid caffeine, alcohol, and large meals close to bedtime.
  • Exercise at the right time: Daytime exercise improves the synchronization of internal rhythms, while intense exercise at night can make it difficult to rest.
  • Create a relaxing routine: Reading, meditation, or a warm bath before bed help prepare the body for sleep.

Circadian Rhythm and Chronic Diseases

A growing body of research indicates that the circadian rhythm not only regulates daily well-being, but also influences the prevention and progression of chronic diseases:

  • Type 2 diabetes → increased risk if you eat at night.
  • Obesity → irregular schedules promote excess body fat.
  • Cancer → some studies suggest that chronodisruption affects cell repair.
  • Neurodegenerative diseases → disruption of sleep and internal rhythms worsens the progression of dementia.

Conclusion

The circadian rhythm is a fundamental pillar of health that goes beyond sleep: it regulates metabolism, cardiovascular function, mood, and cognitive well-being.

Ignoring this internal clock increases the risk of insomnia, obesity, diabetes, hypertension, and depression. But the good news is that we can protect it with simple habits:

  • Natural light in the morning.
  • Regular sleep routines.
  • Eating at the right times.
  • Daytime physical activity.
  • Reducing screen use before bed.

Respecting your biological rhythms not only improves your rest, but also your physical, mental, and emotional health. In short, taking care of your biological clock is taking care of yourself..

Illustration of a clock representing our body's circadian rhythm.

Written by Sara Montaner. We rely on AI technology.

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