Or a natural lark who works evenings and nights?
An out-of-sync body clock can raise your risk of cancer, heart disease and type 2 diabetes, and lead to weight gain, according to new research.
It was reported last month that women who sleep in bedrooms with more light were more likely to be obese — possibly because bright light at night confuses the body clock, which in turn may affect appetite and metabolism.
And leading sleep scientists have warned that the demands of our increasingly 24-hour society mean we’re constantly over-riding our body clocks.
‘Many people don’t even realise they’re sleep-deprived,’ says Russell Foster, professor of circadian neuroscience at Oxford University.
‘But if you need an alarm clock to wake in the morning, you probably don’t get enough sleep — and are out of sync with your body clock.’
So, what does the body clock do and why is it so important to health?
Here we reveal the latest on this still emerging science …
Do you always feel tired and unwell?
Whether you’re a lark or an owl is known as your chronotype. It’s not known why humans show such a broad variation compared with other species, which share a similar chronotype.
‘It may be that in human society there was an advantage in having some people vigilant at night and others in the early hours,’ says Professor Foster.
The body clock’s most obvious function is to tell you when to get up and when to go to bed.
But it also has a role in everything from your metabolism to regulating blood pressure, muscle control and body temperature.
This is why an out-of-sync body clock not only makes you feel tired but could make you ill.
‘Disrupting the body clock is linked with disruption to the cell division cycle — which is the process that produces new cells from old ones — and cancer occurs when something goes wrong when cells divide,’ says Dr Akhilesh Reddy, consultant neurologist at Cambridge University.
It may also be that the stress of going against your clock is what causes the damage.
As Professor Foster explains: ‘To get up at a different time than we naturally wake up, for instance when our alarm clock goes off, we have to activate stress hormones.
‘This is the fight-or-flight response and it prepares the body for action, so the heart starts pumping faster, we throw glucose into circulation for the muscles to use, and we force ourselves to concentrate more.
‘The problem is, if you repeatedly use this response to over-ride your body clock, you’re activating this stress response for extended periods and we know this suppresses the immune system.
‘So, it may be this is what makes you more vulnerable, and allows disease to take hold.’
How it can give you wrinkles
We all have a ‘master’ body clock in our brain, known as the suprachiasmatic nucleus, an area about the size of a grain of rice in the base of the brain.
‘This central clock sends out synchronising signals to the rest of the body,’ says Dr Simon Archer, a chronobiologist at the University of Surrey.
‘There are cells and genes that act as clocks in all major organs and tissues — the kidneys, the liver, even the skin — and these are synchronised by the central clock.’
Last year, Spanish researchers discovered the skin’s ‘clock’ meant genes that protect us from the sun are most active in the day, while genes that encourage production of new skin cells work in the evening.
The researchers suggested that disruption to this clock could lead to premature wrinkles.
Why you can’t face breakfast
Outside cues such as daylight and eating and drinking keep us in time with the 24-hour day.
However, our body clock has an ‘intrinsic rhythm’ it wants to run at, says Dr Archer.
Larks — who prefer early to bed, early to rise — have a faster cycle, while owls, who like staying up and getting up late, are slower.
Larks like to get up earlier because the hormones that make us alert, such as cortisol, kick in earlier, says Dr Archer.
‘However, they feel tired quicker and tend to function best in the morning.’
It takes owls longer to get going in the morning, as their body clock has to be advanced by signals from the outside world.
A key sign of being an owl is not wanting breakfast first thing, says Dr Archer.
‘Our bodies suppress appetite while we’re asleep, then it kicks in again once we’ve woken up — but this process would happen slightly slower in owls.’
Owls are more alert later in the day, and don’t tire as easily at night, because the release of melatonin, the hormone that makes us feel sleepy, occurs later.
Larks are affected more by lack of sleep — feeling tired more quickly if sleep-deprived.
‘They are more sensitive to “sleep pressure”,’ says Dr Archer.
Emails in bed make you ill
Our preference for morning or evening and how much we need to sleep is, to a certain extent, in-built.
As Dr Archer says: ‘There are dozens of genes involved in making your clock work.’
One in particular, Period-3, has been identified as key to whether we’re a lark or an owl by Dr Archer and his team at the University of Surrey.
‘You can have a long or a short version of it,’ says Dr Archer. ‘And you have two copies of it — one from your mum, one from your dad.
‘We have found people who had two long versions of it tended to be larks and people with two copies of the short version tended to be owls.
‘About 10 per cent of people have the lark combination, while 45 per cent carry two of the night owl variant.
‘Everyone else has one of both, so have some characteristics of both early and late types.’
Indeed, Professor Jim Horne, of the Sleep Research Centre at Loughborough University, says it’s easy to convince ourselves that we’re more of a morning or evening person than we actually are.
‘Rather than being “late” types, people who think they are owls may be over-stimulated late at night, whether that’s by too much caffeine, bright light from screens or because they’re reading emails and using technology in bed.’
Professor Phyllis Zee, director of the Centre for Sleep and Circadian Medicine at Northwestern University, says: ‘Getting lots of light late at night may confuse the signals to your body clock.’
In other words, you may not be a night owl at all — you don’t feel sleepy because you’ve confused your clock. And this could also mean other functions are disrupted, leaving the path open for disease.
Before electric lights the difference between larks and night owls would have been much less noticeable.
‘We’re no longer outside for most of our day, and can have light on all the time if we like, so we deprive our body clock of signals that synchronise it with the outside world,’ says Professor Till Roenneberg, a chronobiologist and sleep researcher at the University of Munich.
He says this is to blame for more extreme differences in our body clocks. ‘The genetic variation in our body clocks is becoming amplified.
‘Some extreme larks start their biological day six hours earlier than most people and some extreme owls start their day six hours later.
‘In the past, we would have been much closer together — maybe only a couple of hours apart.’
Should you go into work late?
In theory, there’s no problem for health with our body clocks getting earlier or later – if you can live according to that schedule, says Professor Roenneberg.
Professor Foster agrees. ‘I’ve often thought City banks could screen prospective employees according to chronotype, aligning them with the time zones they work across — so larks could work on Asian markets and owls on American ones.’
But, though the timing of our body clocks has changed drastically, our working hours — and therefore our waking hours — haven’t.
So night owls, who stay up later because they don’t feel tired, are unlikely to get enough sleep before they have to get up for work.
Being chronically sleep-deprived may explain why owls are more likely to over-eat, smoke and drink, in a bid to perk up or wind down.
Ways to trick your body clock
While there’s nothing you can do to change your genetic chronotype, there are ways to control your lark or owl tendencies, and keep your health on track if your working and social life demand it.
‘Bright light is the most powerful way of shifting the body clock,’ says Professor Foster. So, if you’re an owl who has to get up early, get as much light as possible in the morning.
Sleep with your curtains open or blinds up and get up and out for a walk or a run first thing, says Dr Guy Meadows, author of The Sleep Book.
‘You could also sit and eat breakfast with a light-therapy lamp on you as this helps to release the waking hormone, cortisol.
‘To give owls the best chance of winding down earlier, they should avoid being too active in the evening and keep lights dim — and don’t turn on a bright bathroom light to brush your teeth just before bed.
‘Larks who need to work late should do the opposite — making their evenings active and stimulating, for instance by going to the gym, and keeping bright lights on.’