How your body clock governs your weight, health and sex life

A major new series – continuing in The Mail on Sunday – by an Oxford professor who’s studied the subject for 40 years

What do the words ‘body clock’ mean to you? Something you associate with jet lag and feeling out of sorts after a long-haul flight? Or the ticking of a woman’s biological clock? Or the fact some people function better first thing in the morning — and others later at night?

In fact, our body clock controls all of these very different things and much more, as I have discovered over the past 40 years working in this fast-emerging field.

Our body clock sets the very rhythms of our lives, affecting everything from how clearly we think and when our digestive systems are ready for food, to when our muscles are at their strongest and whether we will develop cancer. It affects our sexual compatibility, when we feel symptoms of illness, and the most effective time to take medication. It affects our decision-making skills and even how we communicate.

the clock controls our body’s daily (or ‘circadian’) rhythm in a 24-hour cycle. In so many cases, our ability to succeed or fail — including, for instance, dieting to lose weight — depends on whether we are working with or against these 24-hour cycles.

In this unique series for the Daily Mail and the Mail on Sunday, I will explain how to harness these circadian rhythms to revolutionise your health. today, the focus is on diet, exercise and immunity. tomorrow, I will reveal the lifechanging new understanding about why symptoms of illness are worse at different times of the day and night — and when you should take your medication.

Make sure you read Monday’s Mail to see how your body clock could be affecting your relationship and sex life. the most obvious example of our body’s daily 24-hour rhythms is our sleep/wake cycle. this is tightly regulated by the body clock — which means that if we’re not asleep or awake when our body expects it, it can have major consequences. Sleep is essential for health and yet too often the importance of sleep is disregarded.

the trouble is, most of us assume we can do what we want, whenever we want. this assumption underpins modern 24/7 society, dependent upon night-shift workers to stock our supermarkets, run our global financial services, protect us from crime and, of course, care for the sick.

But night-shift work is not the only disruptor of our sleep and, consequently, of our body clock: many of us who work ‘normal’ hours curtail sleep as we try to squeeze more activity into a schedule that is already bursting at the seams.

We are, of course, not able to do what we want whenever we choose. For our bodies to function well we need the correct materials in the right place, in the right amount, at the right time of day.

thousands of genes must be switched on and off in a specific order. Proteins, enzymes, fats, carbohydrates, hormones and other compounds have to be absorbed, broken down, metabolised and produced at a precise time for growth, reproduction, metabolism, movement, memory formation, defence and tissue repair.

all this requires our bodies to be prepared and ready at the right time — without precise regulation by an internal clock, our entire system would be in chaos. So what is the body clock? Our circadian rhythms are run by a master clock located within our suprachiasmatic nuclei (SCN) in the brain. they tick away independently, generating a rhythm of around about 24 hours. however, it is only around about 24 hours: they tick a little faster or slower, depending on the individual.

In this way, circadian rhythms resemble the mechanism of a grandfather clock which needs a daily adjustment. Without this resetting, the master clock in the brain will drift out of alignment with the 24-hour day.

and it’s more complicated than just one body clock. the SCN is our ‘master clock’, but we also have clocks within the cells of the liver, muscles, pancreas, fat, and probably every cell of the body — and all these other body clocks keep time with the master clock.

think of the circadian system like an orchestra: when all the musicians are playing in sync, you get a symphony. But if they’re playing off-beat, which is what happens if the master clock isn’t set to the same time as all the cellular clocks, you get a biological cacophony, and the whole system begins to break down.

Your SCN body clock needs to be reset on a daily basis and key to

this is light, especially around sunrise and sunset — we call this process ‘entrainment’.

The eye detects dawn and dusk to entrain our SCN, which then sends out signals to keep all the other circadian clocks ticking at the right time, ultimately keeping the ‘internal day’ entrained to the 24-hour astronomical day.

That is why it is so important to expose ourselves to natural light in the mornings and dusk in the evenings, in order to keep our clocks ticking on time with each other. The most effective way to set your body clock is to experience natural light 30 to 60 minutes after sunrise and before sunset. (Light exposure later in the day, until noon, will also help — it’s just that sooner after sunrise is most effective).

I’m the last person to get up at dawn to herald the sun, but when I do wake, the first thing I do is open the curtains; I’ll also eat breakfast by the window. It doesn’t matter if it’s overcast because the light-sensitive cells in the eye ‘add up’ the light they receive (it just might take longer than on a bright day to get the message).

Interestingly, small inherited changes in our clock genes have been linked to whether we are a ‘morning’, ‘evening’ or ‘intermediate’ body-clock type — or ‘larks, ‘owls’ and ‘doves’. (Doves wake between 7am and 8am and want to go to sleep from 10pm to 12am).

Larks make up ten per cent of the population; owls, or evening types, account for 25 per cent of us, and the rest, in the middle, are doves. Larks like to sleep early and get up early, and it seems they have faster body clocks. By contrast, owls have slower clocks.

Together with light exposure, a regular pattern of sleep and wake (i.e. not getting up or going to bed later than your norm) is instrumental in keeping all these clocks ticking in time (eating at regular times is also important, as I explain on the next page).

Disturbing these patterns can lead to a phenomenon we call sleep and circadian rhythm disruption or SCRD — and this condition sets us up to be vulnerable for all manner of ill health.

Whether you’re a titan of industry putting in early mornings and late nights on a deal, or the parents of a baby dealing with feeding all night, the lack of sleep you experience puts your body under threat.

Part of the problem is that poor sleep can put your body’s response to stress (the ‘fight or flight’ response) into overdrive — pumping adrenaline and cortisol, as well as energy-giving glucose, into your system. These hormones raise your heart rate and blood pressure and prepare you to deal with an aggressor (little does your body know the aggressor is an insurmountable pile of paperwork, not a marauding gang or wolf attack).

Over time, it’s like keeping an engine in first gear. First gear gives you that wonderful acceleration. But if you keep your engine in first gear, you’re going to damage it.

The same is true of your body. If you’re constantly operating with an elevated heart rate, heightened blood pressure, and flooding the circulation with glucose, your body cannot run on this sort of ‘emergency’ setting for ever — you are effectively giving yourself longterm stress poisoning.

As a result, some of the most challenging diseases of our time are associated with SCRD. For example, the raised cortisol levels caused by lack of sleep lead to blood sugar imbalances, obesity and type 2 diabetes; it suppresses the immune system and can even increase the risk of dementia.

Lack of sleep also contributes to dreadful mistakes — studies have shown that after four consecutive night shifts the risk of having an accident of any kind rises by 36 per cent.

In fact, sleep loss has been linked to multiple notable industrial accidents, including the Chernobyl nuclear power plant explosion, the Exxon Valdez oil tanker spill, the explosion of the Challenger space shuttle and the Bhopal chemical plant disaster. It’s not called the graveyard shift for nothing.

YET rather than being recognised as loyal friends, biological rhythms and sleep are frequently portrayed as enemies. What we should be doing is protecting our sleep, not trying to cut it short because ‘sleep is for wimps’.

But if sleep and light exposure are vital, they’re not the only factors that affect the daily resetting of our body clock: eating at erratic hours, drinking too much alcohol and vigorous exercise before bed (see next page) have an impact, too. This is because we’re doing things at times our bodies don’t expect it.

And we ignore our circadian rhythms at our peril. Because what we do when really does matter.

This is life-changing information that until now society has largely ignored. Circadian and sleep health is not taught in our schools or to our medical students. It is also absent in the working environment, in many cases.

It has left the economy in the hands of chronically tired and stressed individuals, and constitutes a major missed opportunity to improve health at every level.

Mahatma Gandhi said: ‘The future depends on what you do today’. And so, I want poor sleep and the widespread disruption of our circadian rhythms to become as anathema socially as smoking has become. I want burning the midnight oil to move — as puffing on a cigarette has — from a fashionable practice to an activity regarded by most as socially unacceptable and irresponsible.

With the right education, I hope our machismo culture of long hours and little sleep will go the way of the ashtray.

For the lives of both wise and foolish people all end in death, but those who are wise to their circadian rhythms will, on balance, live longer, be happier and lead more fulfilled lives. I hope that this series will help you become one of them.