It's tempting to resent the tyranny of the clock, that relentless reminder of time's passage. Yet, even if we discarded every watch and smartphone, we could never truly escape timekeeping. The reason is simple: we are, ourselves, living clocks.
The Inner Timekeeper: More Than Just Sleep
We instinctively understand our body's rhythms. We know the reality of the afternoon energy slump and that a 4am finish will disrupt our rest, hangover or not. But delving deeper into this daily cycle, known as our circadian rhythm, offers profound insight into our fundamental biology.
Professor Debra Skene, a chronobiology expert at the University of Surrey, explains that we are in a constant state of biological flux throughout our 16-17 waking hours. Every minute, our chemical makeup, energy, motivation, mood, and alertness are shifting. "It's a dynamic system," she says, "with various rhythms either peaking, troughing, or transitioning at any given point."
This explains why some of us are natural early-rising larks and others are night owls. These chronotypes are normal genetic variations, akin to some internal clocks running a little fast and others a little slow. Without external cues, we would drift out of sync with the 24-hour world.
Light: The Master Reset Button
The primary signal that keeps us aligned is the cycle of light and dark. "It is the strongest, most consistent signal that all animals have evolved to respond to," states Skene. This is why excessive artificial light at night is so disruptive, confusing our systems much like it disorientates migrating birds.
Your body is always preparing for what comes next. Your master clock doesn't react to you waking up; it has been priming your body for an hour or two beforehand. Cortisol levels begin to rise, providing a glucose boost and the impetus to face the day.
Professor Robert Lucas, Director of the Centre for Biological Timing at the University of Manchester, emphasises the coordinated effort. "A fundamental change, like feeling hungry before a meal, involves motivational shifts in the brain alongside preparatory changes in your digestive system and liver. Your biological clock ensures this coordination."
Disrupt this routine, however, and the system falters. Jet lag is an extreme example, but even eating at midnight has consequences. Skene's research found food metabolised differently at night, leading to higher levels of triglycerides (fats) in the blood compared to a midday meal.
The Rhythms Within: From Gut to Mitochondria
The complexity of our internal timing extends far beyond sleep and wakefulness. Scientists now know our gut microbiome operates on its own circadian schedule, influencing digestion and even neurotransmitter production.
Perhaps most fascinating is the discovery that our mitochondria—the cellular powerhouses—have their own daily rhythms. Research from University College London reveals mitochondria "kick in really hard early in the mornings," says Professor Glen Jeffery. They generate ATP (adenosine triphosphate), the fundamental energy currency of our cells, peaking in the morning to fuel our metabolism.
As the day progresses, mitochondrial activity slows. By evening, they are far less active, which Jeffery links to increased muscle soreness after late exercise. At night, the body may switch to a less efficient, pro-inflammatory energy pathway called glycolysis.
These cellular clocks are also light-sensitive. Jeffery's work suggests sunlight, even on cloudy days, delivers specific wavelengths that help "charge" our mitochondrial batteries, crucial for health and ageing.
Harnessing Your Rhythm for Better Health
So, how can we apply this knowledge? The consensus points to respecting light and routine. While reducing evening artificial light is beneficial, Professor Lucas notes a more practical approach: maximising exposure to bright daytime light. A daily walk outside can help strengthen our natural rhythms, counteracting dim indoor environments.
Routine is key, but it's also personal. Chronotypes and preferences vary, and they can change with age. The universal truth, Lucas concludes, is that "everybody will experience these rhythmic changes in pretty much every aspect of their body."
Understanding this hidden symphony of biological timing—the ebb and flow of hormones, energy, and cellular activity—allows us to work with our nature, not against it. By tuning into our body's innate clock, we can navigate our days with greater ease, energy, and wellbeing.
