1. Embrace randomness

Nassim Nicholas Taleb

Have you ever had a weeknight dinner with a suburban commuter? Odds are that the schedule will be imprinted in his consciousness. He will be tightly aware of the clock, pacing his meal in such a way that he doesn't miss the 7.08. He will cut the conversation short at 6.58am, offer a handshake and zoom out of the restaurant to catch his train.

Now deprive him of his schedule - or randomise the departure times of the trains. He would then let the meal follow its natural course, then take a leisurely walk to the station, where he would have to wait for the next train. The time difference between the two situations would be little more than a quarter of an hour. Compare his condition to that of another diner who has to use the subway to go home, for an equivalent distance, but without a known and fixed schedule. Subway riders have a freer schedule, and not just because of the higher frequency of trains. Uncertainty protects them from the stress of optimisation.

The same thing applies to your visit to the gym: imagine spending the day knowing that at 5.15pm you will need to subject yourself to 45 minutes of exercise - whereas our ancestors worked out without schedule and bossy personal trainers, just in response to random impulses from the environment.

Randomness, usually a bad thing (say, in financial markets or in climatic conditions), can be beneficial in some domains. A slightly random schedule prevents us from optimising and being exceedingly efficient, particularly in the wrong things. The pressure to be optimal in their enjoyment of things causes people to suffer distress. When people have the misfortune of being both successful and optimisers, everything is 'organised' with optimising intent: lunch at 12.45pm with the president of the company, the Stairmaster at 4.40pm, and opera at 8pm. So they are punished by success: I am convinced that we are not made for clear-cut, well-delineated schedules. We are made to live like firemen or cheetahs, with downtime for lounging (possibly meditating) between calls or attacks, under the protection of protective uncertainty. Regrettably, some people might be turned into optimisers by their parents, like a suburban child having his precious weekend minutes squeezed between karate, guitar lessons, and religious education. It kills their ability to meditate - their chance encounters with nature's gifts.

If still unconvinced about the role of randomness, consider the following. Would you like to know with great precision the date of your death? Would you like to know the identity of the criminal before the beginning of the movie?

We need to inject unpredictability and surprise into our exercise, work, meditation, private encounters. Make your exercise of random length, avoid closely spaced appointments to leave room for last minute schemes, avoid rigid schedules, and enjoy being just what we are meant to be: humans.

· Nassim Nicholas Taleb is the author of The Black Swan (Penguin, £8.99). This piece is adapted by the author from his book Fooled by Randomness

2. Eat breakfast

The breakfast-free diet, despite requiring cast-iron discipline, is entirely counterproductive. Without breakfast the body goes into 'starvation mode', causing your metabolic rate to slow down and store more fat. Result: you gain weight, rather than lose it. And after 12 hours without food, you're also much more likely to reach for instant-energy snacks. Eating healthily first thing in the morning kick starts the metabolism and stabilises blood sugar levels, giving the body more energy and a controlled appetite.

3. Don't fear the hospital

A recent BBC poll suggested that nearly one-third of the UK population would avoid a hospital visit for fear of contracting one of the many media-hyped 'superbugs'. However, for people under 65 at least, you've got more chance of dying from a lightning strike than MRSA. If you feel there's something wrong, don't delay seeking medical help - avoiding hospital-based diseases could only leave a far nastier disease undiagnosed and untreated.

4. Move to Dorset

Location, location, location: geography can have a profound effect on your health. People living in Dorset are more likely to live to 75 years old than anyone else in the country, with 78 per cent of men and 86 per cent of women reaching that ripe old age. Mancunians, however, have the worst lot, with only 52 per cent of men reaching 75.

If relocating to the southwest doesn't strike you as a bold enough move, perhaps you should consider leaving our obesity-plagued island for one of a number of more healthy options. Research in 2007 by Men's Health magazine found the Netherlands to be the fittest country, Spain the least stressful and Portugal to have the best diet. Meanwhile, Japan seems to be combining the best of all three: it has had the highest average life expectancy of any major country (currently at 82 years) for decades.

5. Floss

Although the effects fast food, smoking and a lack of exercise have on heart disease are well known, we rarely make a connection between gum disease and a heart attack. Medical researchers, however, have: a Howard University team published a report earlier this year proving that periodontal disease allows dangerous inflammatory substances to flood into the bloodstream, clogging the arteries and dramatically increasing the risk of cardiovascular trouble. A trip to the dentist might be as good for your heart as it is for your smile.

6. Stretch

Back pain is the second most common reason for time off work in the UK (just behind the common cold), and costs British industry more than £5bn and the NHS £480m every year. So get up, have a stretch and walk around at regular intervals during the day. Strong core muscles around your stomach and lower back can also help protect you from injury, so doing sit-ups and low-impact back workouts can keep your spine on the straight and narrow.

7. Make new friends
Danny Wallace

There is a wonderfully American expression that at first seems a little trite and silly: 'Strangers are just friends you haven't met yet'. I like it, despite the fact that it's a little unsound. I mean, statistically, some of them are bound to be muggers.

But I think it says something important about our attitude to people we don't know. We're suspicious. Naturally dubious. Who are these people? What are they thinking? What are they doing here? And at precisely the same moment we're thinking that, they're looking at us, thinking: 'Who's that? What are they thinking? And why are they staring at me?'

And so we all go about our daily business, studiously avoiding eye contact as if it carried a five-year jail term, maintaining our silence on trains and buses even when we've stepped on someone else's feet, locking our doors and closing our curtains and falling asleep in front of our tellies.

But over the years I've started to realise that, actually, it's OK to talk to people you don't know. To enter their lives for a brief moment. To talk about the weather, or Wimbledon, or the jaunty hat they're wearing. To make a new friend, even if only for a moment.

Apparently, lonely people are more likely to suffer from stress. They're more likely to develop Alzheimer's, and have a higher chance of developing heart disease. They're also more likely to buy Findus crispy pancakes and only one ticket for the opera.

Thinking about this, a couple of years ago I printed around 1,000 stickers, which I placed all over London. They read, simply, 'Call Me! Let's Have a Polite Conversation!' and underneath featured my mobile number. I mentioned this in a newspaper, and that day received hundreds of calls from all over the country. I spoke to strangers about whatever they wanted. Kaftans. Relationships. Fruit. Puppies. Some calls were from people who felt lonely... But equally, others were from people who felt like taking a chance. Casting their line out and seeing what came back. And each phone call did feel, as I'd hoped it would, as if a fleeting friendship had somehow been made.

Once, I tried simply starting conversations in the street. Initially there was suspicion, but soon I developed a handy technique. It was as much to do with body language as anything else. Step into someone's space politely, say something unusual but nice, then step out and see if they invite you back. It worked. I spoke with strangers that day about everything from shoes to charcoal briquettes. And it never felt odd. Or strange. Or suspicious. It felt like recapturing a right we'd somehow given up a long time ago, when villages became towns, and towns gave way to cities.

The world becomes a far friendlier place when you become a friendlier person. It's easier to find the positives in life. And as well as making other people feel good for however long or short a time, you feel good too. Like the world is less lonely. People make each other happy. And with so many people out there, there's a lot of happiness to be had.

· Friends Like These by Danny Wallace is out now, (Ebury Press, £11.99)

8. Work on your tan

Many of us are forced into the shade or, worse, indoors during the balmy summer months by a justified paranoia over skin cancer. However the sun's benefits far outweigh its dangers if treated with respect. While the act of sunbathing itself is thought to combat depression and aid sleep, the healing properties of vitamin D, produced by the body upon exposure to the sun's UVB rays, have been linked to a decreased risk of everything from high blood pressure to diabetes and cancer (including, intriguingly, skin cancer). Even the most healthy of diets will not give you nearly enough of the vitamin, so try to get yourself outside on sunny days, and definitely avoid the sunscreen (this blocks out the UVB rays). The key is to make sure you only stay out in the sun for as long as you think your skin can handle - around 20 minutes a day for those with very fair skin, or up to an hour for the bronzed or dark-skinned. Sunburn, particularly in young children, is the real carcinogen, so as long as you're careful there's no need to worry.

9. Buy a full-length mirror

Vanity can have some unexpected benefits. Not only will you avoid bad-hair days, a check-up in the mirror can reveal early symptoms of some cancers before they become life-threatening. Testicular cancer is the most common cancer in young men, so even if you feel fit and healthy it's worth checking for any unusual lumps and bumps (an abnormal lump will feel like a hard pea). Women over the age of 40 are advised to undergo a mammogram every year, while younger women are encouraged to have a clinical breast examination annually, yet it's still worth checking for lumps every month or so to be safe. Skin cancer can be harder to spot, but if you find a new mole that is asymmetrical, blotchy or multicoloured see your GP. Get to know your body so any changes become immediately apparent and don't be afraid to visit your GP if something unusual appears.

10. Don't follow fad diets

Fad diets promising quick results may seem a tempting way to shed a few pounds, but try to resist. Crash dieting will slow your metabolism, making you much more likely to put the weight straight back on. Celebrity 'detox' diets can even cause vitamin deficiencies, muscle breakdown and blood sugar problems. A far healthier diet is to cut down on high fat foods and make sure you get enough fruit and vegetables.

11. Ring your mum

Many diseases are now thought to have some sort of genetic basis, so if you can quiz your parents or relatives about what might run in the family it will mean you'll know what to look out for and it might even force you to finally make that lifestyle change you've been putting off. Those with a family history of breast or colon cancer can request a genetic test from the NHS, to tell you whether you're hiding any

12. Get married

Although frequent contact with friends, family, neighbours and even pets boosts the development of the brain and the immune system, and provides other major health benefits, the biggest improvement to your health and longevity comes from finding your significant other and getting hitched. Research suggests that getting married could extend a man's life by as much as seven years and a woman's by two years.

13. Do the crossword
Jonathan Crowther

Setting crosswords is a solitary activity. I know of a few setters who habitually work in pairs, but the great majority work alone. It is also largely sedentary. I myself spend hours on grids and clues sitting at my desk, getting up only occasionally to consult a reference book on the other side of my study, change the CD on the player, or, once in a while, seek out my non-crossword-solving wife to try out an idea on her.

After more than 36 years as Azed, it has become a routine part of my life that is constantly stimulating, though I am conscious of the need to balance it with more physical activity and have learnt to recognise the signs of mental weariness that warn me to close the dictionary and lay down my pencil for a while. It is remarkable how effective even a short break from crossword work is in refreshing the mind when one returns to it. I know from experience that the same goes for crossword solving.

So crosswords, especially cryptic ones like mine, challenge the mind of both setter and solver. But are they good for you? Common sense says yes, and this is borne out by both anecdotal evidence and scientific research. There is unmistakable satisfaction, and hence a feeling of wellbeing, to be had from completing a challenging, but fair, crossword puzzle (though whether, conversely, being defeated by one that is too difficult or badly clued raises the blood pressure is at least arguable). The regular feedback I get from solvers, through the special nature of the monthly Azed competitions, tells me that many of them look forward eagerly to the weekly challenge my puzzles present (and are even disappointed if they solve them too quickly!). A regular competitor once described tackling the Azed crossword as his 'weekly mental punchbag'.

It has become clear to me, in recent years, that younger people are less attracted to crosswords than they once were, and more to perhaps less demanding brain-stretching activities such as Sudoku and similar logic puzzles. Whether or not one approves of this trend, the average age of your crossword solver is now probably higher than it was ten years ago. So it is reassuring to read research that appears to show the beneficial effects crosswords have in warding off neural decline in older people.

According to the findings from one experiment with a group of pensioners in the US: 'While physical exercise did not seem to delay the onset of Alzheimer's, intellectual exercise did. Those who did four crossword puzzles a week were less likely to get the disease than those who managed only one.'

Lest too much be read into this, here is a further quote, from an overview of research work on mental deterioration: 'Several studies have found that folks who regularly engage in mentally challenging activities - like reading, doing crossword puzzles or playing chess - seem less likely to develop dementia in later life. The difficulty comes in figuring out whether their good fortune is a direct result of their leisure activities, or whether their continuing pursuit of those pleasures merely reflects good genes for cognitive function.'

On a lighter note, Michael Frayn wrote in his foreword to Chambers Book of Azed Crosswords (2005): 'Here are a hundred of the precious pills all at once. And if one a week keeps the geriatrician away, a hundred together (perhaps taken in conjunction with a few bananas and bars of dark chocolate) must surely be the elixir of youth.'

· Jonathan Crowther is the compiler of The Observer's Azed cryptic crossword

14. Turn a vice into a virtue

Rather than anxiously raising your stress levels over every unhealthy indulgence, relax; pleasure itself can keep you healthy. Not only will it torpedo stress, it also causes our cells to release a natural antibiotic: enkelytin. Many researchers also believe that small doses of stressors, whether from a few drinks at the pub or a chocolate bar, can reverse the ageing process. These stressors kick-start our natural repair mechanisms to fix the damage we've caused, and, as long as the damage is not too severe, they may overcompensate, repairing unrelated damage caused by ageing.

Evidence for this hormeosis effect is growing - one large-scale study tracked 28,000 nuclear shipyard workers over eight years to study the effects of low doses of radiation, and discovered that the mortality rate was 24 per cent lower than a control group of 32,500 ordinary shipyard workers. One influential biologist claims that once we've mastered this trick, and found the exact level at which a small dose becomes dangerous, it could stretch the average human lifespan to 90. What's more, many of the health fraternity's traditional bugbears contain some surprising secret benefits - chocolate contains flavonoids, which lower blood pressure; coffee is a good source of antioxidants and there is evidence suggesting it can reduce the risk of Parkinson's, type-two diabetes and liver, skin and colon cancer; alcohol's beneficial effects, if the hundreds of medical journals are to be believed, are numerous. The key is always moderation - a little pleasure goes a long way.

15. Shed the guilt

Taking up a healthy lifestyle can be challenging and falling off the wagon every now and again is normal. The danger begins with feelings of guilt, getting annoyed with yourself every time you reach for a piece of cake or skip the gym. This guilt can make you far more likely to think, 'now I've blown it, I might as well give up altogether' and ruin all the hard work you've put in. Just accept that no lifestyle change is ever 'all or nothing'.

16. Watch what you sleep

As our lives become more and more hectic, a good night's sleep can often be the first thing to go. Without it, we can suffer mood swings and increase our risk of diabetes, cardiovascular disease and obesity. But how much do we actually need? Everybody is different, but a Californian study of more than one million adults over a six-year period discovered that seven is the magic number. Those who slept seven hours per night had the lowest mortality rate, while those who slept more than seven hours had the highest. Too little sleep could be bad for you, but too much seems to be even worse.

17. Eat bananas and garlic

Forget expensive superfoods, the simple (and cheap) combination of bananas and garlic can have significant health benefits. A study by mental health charity MIND found that the serotonin in bananas can alleviate symptoms of depression. Indian researchers also discovered that eating two bananas a day for one week can reduce your blood pressure by 10 per cent. Meanwhile, a study in the US found that eating garlic improves circulation. Of course, you don't have to eat them together.

18. Become a clock-watcher

One in six people in the UK work more than 60 hours a week - a worrying amount that will lead to stress-related problems later in life - so make sure you leave on time. While you're at it, if you're feeling under the weather take a day off. A recent study showed that employees who come into the office feeling unwell are, on average, 72 per cent less productive than usual, and risk making the illness worse.

19. Integrate exercise into your routine

The latest NHS guidelines recommend that a minimum of half an hour of moderate exercise each day is needed to offer good health benefits. For those of us who find half an hour difficult to spare, there are ways to incorporate it into our everyday lifestyle: walk or cycle to work rather than drive, or get off the bus a stop early; use the stairs instead of the lift; do some sit-ups or push-ups in front of the TV; use your lunch break as an excuse for a brisk walk to the shops and back. On your weekends do a good long spell of gardening or pick up your tools for a bit of DIY - as well as losing that stubborn beer belly, you might even end up with a decent lawn or a set of shelves.

20. Get happy

Stress is a modern epidemic. It is linked to every leading cause of death in the UK, from cancer to heart disease. Nearly one-in-ten of us now report that we are experiencing work-related stress to the extent that it's making us ill, and every year around 12 million adults report to their GPs with mental health problems - of which the vast majority are stress-related. It seems like we could all do with a bit of cheering up.

Richard Layard, a leading figure in what has become known as 'happiness economics' and the author of Happiness: Lessons from a New Science, believes the secret to long-lasting happiness lies not in those old Protestant benchmarks, hard work and prosperity, but in reassessing what is important to us.

As our wealth increases, our actual happiness, as measured by stress levels and surveys on mental heath and emotional self-recognition (essentially being asked 'Are you happy?'), drops. Thus, despite the fact that we're richer, safer and healthier than ever before, the aforementioned stress problems are through the roof, our level of trust in others has dropped from 60 per cent to 30 per cent in the past 50 years, and our children are the unhappiest of any wealthy European country.

Layard, along with several other leading scientists, doctors and politicians, believes we need to stop measuring ourselves in terms of wealth, as this leads to an obsession with competition and diminishes the benefits we draw from our hard work. As we become used to higher income levels, our idea of what makes a good wage rises to unrealistic levels, making us invest more time in work than is good for our happiness - and our health.

So if you are unhappy or over-stressed in your job, ask yourself why you are doing it - according to a 2005 government report, employment can improve self-esteem, quality of life and general wellbeing, but only if it's the right type of work for you.

Take a full lunch hour every day to get a proper break (a recent study suggested only 18 per cent of office workers do), don't forget to laugh (research by the American Physiological Society showed that just thinking about watching a comedy film lowers stress hormones by up to 70 per cent), and find your own method of unwinding. Your heart, brain, lungs, arteries, muscles, nerves and libido will thank you for it.

21. Go with the flow

'Flow' was first posited in the Seventies by Croatian-born psychologist Mihály Csíkszentmihályi as a way of describing a mental state in which a person is fully immersed in what he or she is doing, and in which time is distorted and any awareness of what's going on around you disappears. Also known in the growing world of boardroom and sporting cliches as being 'in the zone', flow is achieved at the point at which the brain is lost to everything but the task at hand. For flow to take place, it's necessary for the task to be balanced with the person's ability level - too easy and it will be boring, too hard and the task will be stressful. Reaching this mental state can bring an end to stress at work, and is often seen as the goal of meditation and certain types of yoga. Finding a career, or pastime, that fits with your abilities and interests is the first step.

22. Get a little muddy

While the thought of germs crawling about kitchen surfaces may keep the hygiene-conscious awake at night, the truth is that our modern ultra-clean lifestyles may be harmful. Cases of asthma, hayfever and other allergies have risen in urban areas over the past 50 years (rural regions remain largely unaffected). Many put this alarming trend down to the 'hygiene hypothesis' - we're now so germ-free that our immune systems don't get the chance to train themselves to deal with the microscopic critters; so every time a relatively harmless irritant makes its way into the body, the immune system overreacts, forcing us to sneeze, cough or scratch to get rid of the perceived threat. In June this year the EU launched a study of 7,000 children across hygienic Finland and Estonia, and the more germ-friendly north-west Russia to test the theory.

23. Take a break

Over the next year the government will complete the increase in the minimum annual holiday entitlement for full-time workers from a measly 20 days up to 28, and it's up to us to take advantage. A summer holiday can do wonders for your health, as long as you do it properly. Don't charge around sightseeing as if you're on a deadline, give the brain time to relax - the constant strain put on it by frenzied multitasking at work can be reversed by a relaxing two-week break. The food we eat on holiday tends to be healthier, as we opt for lighter salads and fish in the burning sun rather than stodgy, starchy food, and this, combined with more sleep and exercise through swimming or a walk round the sights, can lead to a noticeable drop in blood pressure, a boost to your immune system and even an improvement in memory.

24. Break out the Barry White

Although regular sex has long been known to improve self-esteem and combat stress, leading to a longer, happier life, there may be many more healthy reasons to dim the lights and move to the bedroom. During an orgasm the body produces the hormone oxytocin, which battles against insomnia, encouraging a more restful night's sleep, and improves intimacy and bonding within a relationship (oxytocin is also released when women give birth as part of the mother-baby bonding process). Perhaps unsurprisingly, studies in which couples were asked to go without sex for a period of months found that the strength of their relationships generally declined rapidly. Oxytocin has also been linked with pain relief, and the endorphins released during sex only compound this painkilling effect: there are reams of evidence suggesting that sex can soothe everything from PMS to lower back pain. Having sex once or twice a week can also boost your immunity to disease, as it is linked with higher levels of a natural antibody, immunoglobin A (IgA), which can protect you from colds and other infections, and, according to a report in the British Journal of Urology, men who ejaculate frequently in their twenties reduce the risk of getting prostate cancer by one-third. All this and a pretty good workout to boot ...

25. Gossip
Oliver Marre

Gossip is widely assumed to be bad for your soul. Whispering about other people, giggling behind their backs, passing on stories that can only annoy the characters featured in them - not, morally speaking, a particularly edifying way to spend your time. But it can certainly be fun and, unlike so many of mankind's more exciting activities, this one is good for your health.

Think of a funny story that someone told you about the person who sits opposite you at work. Back when you first heard it, you no doubt had a good laugh. Bingo! That boosted your immune system and, according to research presented at this year's annual meeting of the American Physiological Society, reduced the amount of the hormone cortisol flowing round your body, which will have lowered your blood pressure and softened your arteries. Even today, it probably brings a smile to your face. That little twitch of the lips means you have just been exercising about 16 muscles in your face - postponing the need for a facelift by several minutes. You've also just increased your body's production of endorphins, which are natural painkillers. At the same time, you've been signalling, as your cave-dwelling ancestors used to, that you're not a threat to those around you, enabling everyone to relax.

Now consider another piece of gossip you heard recently. Take something a little less funny, but that demanded a good 10 minutes of analysis by the water cooler. That break got you away from your computer, which would have helped avoid Repetitive Strain Injury, given your eyes a screen break and enabled you to stretch your legs, helping blood flow. Most importantly, though, it would have enabled you to make friends.

Gossip, by its nature, pits the many against the few and being on the side of the many is a good thing: the detrimental effects to the health of those unfortunate people who are the subjects of gossip (stress, for example) rather than its practitioners is insignificant in scientific terms, because more people will benefit than will suffer. The excitement of sharing gossip produces endorphins and, in a nod to the maxim that nice guys finish last, studies have shown that as you get older, remaining socially active - invited out and engaging in the mental stimulation of gossip - can extend your life by six years.

But a word of caution: be careful if you gossip about someone bigger than you. A bash on the nose can have adverse effects.

· Oliver Marre is The Observer's diarist Pendennis.