The secrets of the body clock: how to tune into your natural rhythms – and have a better day

It’s easy to hate clocks. Their unstoppable forward churn wakes us up and shames us for running late. They are a constant reminder that every enjoyable moment, just like life itself, is ephemeral. But even if we rounded up all our time-telling devices and buried them deep in the earth, we could never escape clocks. Because we are one. ‘The role of light and dark is critical to reset your clock.’Illustration: Spencer Wilson/The Guardian Your body has been preparing to wake up for an hour or two before it happens.Photograph: Posed by model; ArtistGNDphotography/Getty Images Deer change with the seasons – but do humans?Photograph: Jared Lloyd/Getty Images Running at night may make your muscles ache more.Photograph: Posed by model; dusanpetkovic/Getty Images Softer light may be beneficial in the evening.Photograph: Posed by model; Westend61/Getty Images We don’t need to have studied the intricacies of circadian rhythms to know that we are ravenous at certain times and not others, that the mid-afternoon slump is real, and if we party until 4am we’re unlikely to sleep for eight hours afterwards, because the body clock has no sympathy for hangovers. But to better understand this all-encompassing daily cycle is to truly know our animal selves. Most of us are awake for 16-17 hours each day, during which we never stop changing, biologically speaking. Every minute, says Debra Skene, a professor in chronobiology at the University of Surrey, “our bodies are different”. She is referring not just to our chemical makeup, bodily functions and energy levels, but also our motivations, behaviour, mood and alertness. “At every point in time, we’ve got rhythms that are either going up or going down. Some are at their peak, some are at their middle point. It’s a dynamic system.” Some of us are early-rising larks and others are midnight-oil-burning owls, because our intrinsic clocks are unique to us. These different chronotypes, as they are known, are normal genetic variations, says Skene. Some people run a little fast, others a little slow; left unchecked, they would slip further ahead or behind. “Over time, you’d be really desynchronised with life on Earth,” she says, “so the role of light and dark is critical to reset your clock to 24 hours each day.” The light-dark cycle “is the strongest, most consistent signal that all animals have evolved to respond to”. This is why we’re becoming increasingly aware of the negative effects of too much artificial light at night: it confuses our systems, just as it does for migrating birds and sea-turtle hatchlings. While we’re all kept more or less in line by the same 24-hour light cycle, our different chronotypes mean some of us prefer to wake up and go to bed earlier or later than others. Skene’s team found that even if a night owl trains their body clock to comfortably run two hours earlier, by strictly adhering to regular waking, bed, breakfast and lunch times, when they stop that training, “they might drift back to being late types”, in accordance...

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