Posted by reCellorCircadian AM+PM
on November 11, 2025
Reading time: 6~7 minutes
Last Updated November 13, 2025
What Is the Circadian Rhythm?
Our bodies have a built-in "biological clock"—known as the circadian rhythm—that operates on a roughly 24-hour cycle. Everything from sleep-wake patterns, body temperature, hormone secretion, metabolic activity to immune responses is influenced by this rhythm. Simply put, it’s the body’s rhythm of being "active during the day" and "resting at night," synchronized with the external light/dark cycle.
Molecular Mechanisms: How Does the Biological Clock Work in Cells?
At the molecular level, the biological clock primarily functions through the following mechanisms:
A central brain region (such as the suprachiasmatic nucleus, SCN) acts as the master clock, while every tissue in the body also has its own "peripheral clocks."
Inside cells, there’s a transcription-translation feedback loop (TTFL): "clock genes" (e.g., PER, CRY, CLOCK, BMAL1) are transcribed and translated into proteins. As these proteins accumulate, they feedback to inhibit the expression of their own genes, creating ~24-hour periodic oscillations.
These clock genes/proteins not only regulate themselves but also control a large number of downstream genes, thereby affecting cellular metabolism, repair, immunity, and even cell proliferation/apoptosis. For example: The CLOCK/BMAL1 protein complex can activate genes containing E-box elements (including certain clock genes and genes involved in the cell cycle). Thus, the circadian mechanism is not just about "when to sleep/wake up"—it’s a physiological process that penetrates cellular, tissue, and organ levels.
Why Does Circadian Disruption Impact Health?
Circadian misalignment occurs when the biological clock is out of sync with the environment/behaviors (e.g., light exposure, sleep schedules, diet) or when the internal clock malfunctions. Its health implications include:
Metabolism-related issues: Increased risk of weight gain, insulin resistance, and type 2 diabetes. Studies have found that disrupted clock genes affect the metabolic system.
Cardiovascular/immune/inflammatory effects: Clock genes interact with the cell cycle, DNA repair, immune cell function, and inflammatory pathways. Circadian disruption may exacerbate inflammatory responses and weaken immune defense.
Cancer risk: Some research indicates that long-term circadian disruption (e.g., night shifts, frequent cross-timezone travel) is associated with an elevated risk of certain cancers.
Sleep/mental/cognitive function: Circadian misalignment often leads to insomnia, daytime sleepiness, decreased attention, and mood fluctuations.
In other words, the biological clock is like the body’s "time manager." When this manager is disrupted, many systems may "arrive late to meetings" or "miss tasks."
How to "Reset" Your Biological Clock in Daily Life?
Given the close link between circadian rhythm and health, we can maintain or rebuild it through simple lifestyle adjustments:
Regular light exposure: Get natural light during the day (especially in the morning) and reduce exposure to bright, blue-rich screens at night. Light is the most important synchronization signal for the biological clock.
Consistent sleep-wake schedule: Go to bed and wake up at the same time every day—even on weekends.
Diet and exercise: Eat and exercise at regular times; avoid heavy late-night meals or intense early-morning workouts.
Mitigate night/shift work effects: If night shifts are unavoidable, use blackout curtains, adjust diet and light environments to help reset the clock.
Optimize sleep environment: Keep the bedroom dark, quiet, and cool. If you have insomnia symptoms, consult a doctor promptly.
Through these methods, we can align our biological clocks with natural rhythms, thereby improving overall health, boosting work efficiency, and enhancing sleep quality.
Summary
The circadian rhythm (about 24 hours) is a vital cycle that regulates our body’s functions, controlling processes from genes and cells to organs.
It operates through feedback loops between clock genes and proteins, and these molecular mechanisms are closely linked to metabolism, immunity, cancer development, and sleep regulation.
When this rhythm is disrupted—by factors such as night shifts, frequent travel across time zones, exposure to bright light at night, or irregular eating habits—health risks increase.
Fortunately, by maintaining regular daily routines, proper light exposure, balanced diet, and consistent exercise habits, we can “reset” our internal clock and support better overall health.
References
Fagiani, F., Di Marino, D., Romagnoli, A., Travelli, C., Voltan, D., Di Cesare Mannelli, L., Racchi, M., Govoni, S., & Lanni, C. (2022). Molecular regulations of circadian rhythm and implications for physiology and diseases. Signal Transduction and Targeted Therapy, 7(1), 41.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
