There is no louder wake up call than crossing the threshold into middle age.
Turning 40, according to cancer specialist Dr David Agus, is when we begin to question our mortality and take stock of our sedentary, desk-bound lives - and rightly so, given that in our fourth decade we put on weight more easily, get insufferable hangovers, take longer to get fit and recover from injury more slowly.
"This is when we begin to listen to our bodies and avoid the things we know to be bad for us," he says.
All is not lost, thankfully, even if you have spent the past few years sitting on the sofa drinking wine. If we live more healthily and exercise regularly, we can enjoy a longer fuller life, reports Telegraph.
"Disease is often a problem in our fifth, sixth and seventh decades and we can do much to prevent it during our 40s," Dr Agus says.
Life is against us, though, as we reach this midpoint. Our 40s, according to Dr Muir Gray, author of Midlife: Look Younger, Live Longer, Feel Better, are our most challenging decade to date - we're the "sandwich generation" juggling parenting, aging parents and our careers.
"The adventurer Bear Grylls lives a very low risk life compared to those who commute, sit at a desk and stare at a screen," he says.
"All these cause stress and inflammation, which decrease the quality and length of our lives."
In your 40s you have to train more, not just in terms of exercise but in the way you work, eat, relax and sleep, he continues.
"The main problem is stress - you've got to be disciplined in order to cope with life's pressures."
While we can't slow the aging process, if we develop the right attitude we can feel younger and more energetic. "Now is the time to start caring for yourself," Dr Gray says. "Remember: midlife is not the beginning of the end but the end of the beginning."
Drink full fat milk
Particularly after exercise, as this can help combat the reduction in muscle mass associated with getting older, especially once you're in your 50s. It also contains calcium, which is essential for bone health.
Avoid short cuts
Supplements are not only expensive but they can have detrimental effects on your health, warns Dr Agus. Calcium supplements, for example, can increase prostate cancer risk in men. "It's simple - eat real food to stay healthier," he says.
You are not a cow
Research suggests that those who graze are at greater risk of diabetes. "We weren't made to eat all the time, and if we do our bodies become resistant to insulin," Dr Agus says. Avoid eating in front of the television, use smaller plates and put all biscuits and cakes out of sight, says Dr Gray. "Eat slowly, putting your knife and fork down between every mouthful."
Say no to shiny packets
Artificial ingredients from sweeteners to the chemical preservatives in most processed foods accelerate ageing and lead to inflammation and cell death, according to nutritionist Dr Josh Axe (DrAxe.com).
David Marshall, a personal trainer and author of fitness guide Bodydoctor, suggests eating food that requires plenty of chewing with no E-numbers. "If it can be added, it should be avoided," he says.
Inflammation caused by the microbial activity in our gut can cause ageing, particularly of the skin, says Liz Earle, author of The Good Gut Guide. "The healthy bacteria and lactoferrin found in plain live yoghurt can dramatically improve our levels of skin-friendly flora, which in turn leads to smoother, clearer skin, especially for those prone to adult-onset acne or rosacea".
Drink coffee - yes, you can - and tea
While too much caffeine is dehydrating and increases inflammation, there is nothing wrong with coffee in moderation - caffeine is thought to reduce the risk of Alzheimer's and it can also enhance physical performance; personal trainer Marshall suggests a cup before exercise.
Meanwhile teas such as rooibos, black, green and white teas, and oolong teas contain antioxidants thought to combat the ageing process.
Swap red meat for organic white meat, butter for olive oil and go easy on carbs, says Dr Gray, who also recommends purple foods, which contain polyphenols associated with a longer life, and pulses and lentils.
Dr Axe suggests we add turmeric to our diets, which is thought to fight inflammation, arthritis, depression and pain, while Earle recommends almonds and sunflower seeds for their skin-plumping properties.
It's not fat that makes you fat...
... it's sugar, according to Marshall. Sugar also promotes a process called glycation, which damages cells and causes wrinkles. "This doesn't just mean avoiding sugary muffins and chocolate bars but also simple carbohydrates such as white rice and potatoes, which are also sugars," he says.
Tame your tippling...
You don't have to give up booze entirely, says Dr Gray, but it is sensible to have alcohol-free days as you age. His rule is one day a week in your 40s, two in your 50s and so on. "I'm in my 70s and I feel much better if I have four days without alcohol," he says.
... and don't get drunk
Not just because you look more stupid the older you are but because too much alcohol leads to a bad night's sleep. "It's a question of working out how much you can drink and still sleep through the night and then never drinking more than that," says Dr Agus. "I know that if I have one and three quarters glasses of wine I am fine, but we all metabolise differently."
Sleep and mental health
We live longer if we live with someone else, according to Dr Agus, and if we don't we should make an effort to socialise regularly. "Having a partner is critical; life is about having someone to enjoy it with - we tend to do more if we have someone to share it with," he says.
Midlife is a challenging time for the mind and it is essential to find ways to switch off, says Dr Gray. Take a couple of minutes to notice your breathing five times a day and every evening do something that takes your mind off work and the stresses of your life: a long bath, reading a novel, gardening or yoga.
Reasearch by the University of Michigan suggests that taking walks in nature is associated with a whole host of mental health benefits, including decreased depression, improved wellbeing and mental health and lower stress levels.
Stand up at your desk
If you stand for eight minutes of every half an hour you are at work, and move around for at least two minutes, you can experience lower levels of blood sugar and cholesterol, reduced weight and improved concentration, according to a study by Cornell University.
Our bodies thrive on regularity, according to Dr Agus. Try to get up and go to bed at roughly the same time each day and eat at regular intervals for improved mental and physical health.
Sleep cool, dark and quiet
Studies show that those who live near an airport live shorter lives. "The brain needs quiet while it is resting," says Dr Agus, who recommends investing in black-out blinds and ear plugs.
It is essential to focus on getting quality sleep as it has a long-term impact on our physical and mental health as well as our weight and disorders associated with cardiac function and diabetes, agrees sleep specialist Prof Jason Ellis.
"As we age we become more susceptible to night-time wake-ups, so we need to work at creating a calm environment that maximises your chance of a good night's sleep," he says.
No screens before bed
Stop staring at your laptop or phone an hour before you want to sleep - studies have shown that exposure to the blue-and-white light given off by these gadgets prevents our brains from releasing melatonin, a hormone that tells our bodies it's night-time.
If, like Dr Agus, you are not prepared to give up the screen, invest in a pair of "geek" glasses, designed for gamers, with lenses that filter the wavelengths that the brain confuses with sunlight.
No gorging after 9pm
Prof Ellis suggests limiting the amount of food and drink we consume in the hours before bedtime to improve the quality of our sleep.
"Don't down a pint of water before bed; sip water throughout the evening and eat earlier in the evening," he says. "If the body is trying to digest and sleep at the same time, as you get older, digestion wins and you wake up."
Invest in good quality bedding
Your mattress doesn't have to cost a fortune, but it must be comfortable to encourage deep sleep, Prof Ellis says, and the same goes for your sheets and duvet.
While he doesn't recommend sleeping in separate beds from your partner, he does suggest investing in separate duvets to minimise disturbance. "This way you customise the tog and filling," he says. "Don't settle for two single duvets, though; go for two doubles so you never feel shortchanged."
Conquer your snoring
Snoring is one of the major obstacles to a good night's sleep and tends to get louder and more problematic with age. Dr Ellis recommends snorers consider a mandibular advancement device, an inexpensive gum-shield-style contraption, which holds the lower jaw and tongue slightly forward to make more space for breathing and is proven to prevent snoring and mild to moderate sleep apnoea.
A low dose of aspirin daily has been shown to lower the risk of heart attacks and strokes and can also, according to research by Prof Peter Rothwell of Oxford University, cut the risk of developing several cancers.
There are side effects - aspirin can increase the risk of developing a stomach ulcer and cause breathing difficulties, so you should always consult your doctor - but the benefits far outweigh the risks, according to Dr Agus, who also, controversially, believes over-40s should take statins.
And if you do, now is the time to give up. Research shows that those who quit smoking before they turn 44 can live almost as long as people who never smoked. In Britain, smoking is responsible for 96,000 deaths a year, and about half of regular cigarette smokers will be killed by their addiction.
Get real about your skin
A visit to a cosmetic dermatologist is a good idea once you hit 40, to help you adapt your skincare regime to your ageing skin without wasting money on beauty products that don't work, says dermatologist Dr Sam Bunting.
She recommends using a retinoid cream at night, to increase skin cell turnover and stimulate collagen synthesis, while skincare expert Sarah Chapman suggests a serum with antioxidants, peptides and vitamins.
Exfoliate both face and body, to remove dead skin and speed up cell renewal - although be gentle, as after 40 your skin is more delicate.
For a glowing complexion, Chapman recommends acid exfoliants such as lactic acid, while make-up artist Jemma Kidd uses a dry body brush on her legs three or four times a week.
Invest in your hair
You should pay attention to your hair as much as your face once you hit middle age, says Gary Glossman of Josh Wood Atelier. "Hair becomes drier and less supple as it ages, so apply regular treatments such as masks," he says. Cutting a fringe is a great way for women to "anti age" their look, he says, and both sexes should keep their hairstyle current t - it's one thing you can change.
Wear SPF sun cream daily
Sun exposure is the main cause of premature skin aging - ultraviolet light speeds the formation of lines, wrinkles, and sun spots, while damaging the skin's ability to repair itself. Once you're 40, wear at least SPF 15 every day and SPF 30 to 50 during the summer. "It's a good idea to choose one that functions as a primer whilst also protecting from UV," suggests dermatologist Dr Sam Bunting.
Brush your teeth
Gum disease not only causes bad breath but it is linked to heart disease, strokes and diabetes. Brush for two minutes twice a day using an electric toothbrush, floss or use interdental brushes and see the dentist and hygienist as often as they recommend, says dentist Dr Nigel Carter, Chief Executive of the Oral Health Foundation. "There's no point living into your eighties if you've got no teeth to eat with," adds Dr Agus.
Stay away from the knife
Avoid doing anything irreversible to your body, warns Dr Agus. Not only will you have to recover from surgery, which puts strain on your body but it is impossible to know how your cosmetic surgery will age.
Look after your feet
Now is the time to take stock of your foot health, as foot problems can lead to knee, hip and back pain. Cut your toenails regularly, wash, dry and moisturise your feet after washing, and only wear comfortable shoes -no high heels, according to Dr Agus. Alexander technique and Pilates can build up foot strength, which will in turn help your posture.
See your doc and get your jabs
Treat aches, pains and illness quickly to avoid them becoming chronic, says Dr Agus, and keep up to date with your jabs, including the annual flu jab. He also recommends getting your cholesterol checked, as well as your CRP (C-reactive protein, a measure of inflammation in the body), CMP (comprehensive metabolic panel, a measure of liver and kidney function, as well as conditions such as diabetes) and haemoglobin A1c (your average blood-sugar level) once you hit 40
Movement over time equals health, according to Dr Agus. The simple act of walking increases stamina and fitness and reduces stress. "The aim should be 150 minutes of brisk walking every week - take the stairs at work, get off the bus two stops early, anything to make you walk," says Dr Gray.
Exercising shouldn't be painful but it should be uncomfortable for maximum results, according to Dr Agus. "Do yoga and Pilates because you find them difficult, not because you find them easy," he says.
Be an early bird
As you get older, your metabolism begins to slow down - if you exercise earlier in the day you will elevate it for longer, says Marshall, Bodydoctor. "If you exercise just before dinner you will end up going to bed on a stomach full of undigested food and your metabolism will plummet.
Stand up straight!
The bent silhouette of an elderly person on road signs is only occasionally the result of spine disease - more often it is due to poor posture earlier in life. Take up pilates or Alexander Technique and never look at your phone as you walk. Every inch your head is ahead of the true vertical line increases the weight your neck muscles have to hold by 10 pounds. "If you do it for long enough, your head will be permanently poking forward like a tortoise," he says.
'LISS' is more
Low-intensity training (otherwise known as LISS) is not only kinder on joints than HIT - high-intensity training - with less chance of injury, but is proven to be more effective at increasing fitness and psychological health and aiding weight loss.
The intensity of a LISS work out is between 60 and 80 per cent maximal heart rate for at least 40-60 minutes. To establish your optimum heart rate for a LISS workout, subtract your age from 220. Your LISS heart rate will be 60-70 per cent of this figure.
The physiological changes that happen to the body at this age cause loss of muscle, reduction in bone quality and a reduction in maximal oxygen uptake - how much oxygen it can take in and use - which essentially means a smaller "engine", explains older athlete specialist Richard Brennan. All this means you might not perform as well as you used to and recovery will take longer - go with it.
Each decade after 30, our muscles decline by up to 8 per cent. This is why strength training is key for maintaining muscle mass, preventing osteoporosis and burning fat, says David Marshall. "You need to work out all your body, not just parts of it," he says.
Compared to cardiovascular exercise such as running, resistance training burns some 25 per cent more additional calories in the first hour following your workout and may keep your resting metabolic rate elevated for up to 72 hours afterwards.
Track your progress
Wearable technology such as a smart watch or FitBit can be a helpful way to track your steps and workouts and keep you motivated or you could, as Dr Gray recommends, download the NHS Active 10 walking tracker app via nhs.uk/oneyou/apps. "It's not about 1000 steps, it's about moving as much as possible," he says.
Take up a new sport
Now is the time to take up a new sport, according to Dr Gray, to improve your balance and hand-eye co-ordination as you hit middle age. He recommends joining a veteran league - there are cycling, rugby, football and hockey leagues for beginners cross the country (see Sport England) - or taking up a social sport such as golf that can be played into old age.
Get a dog
If you want to get fit, get a dog, according to Dr Gray. A dog provides the perfect antidote to a sedentary life, particularly if you're working from home, while being the most uncomplicated of work-out companions. There are even studies to show that dog owners get more exercise than the average gym goer.
How did you score?
How many of our 40 suggestions are part of your lifestyle now?
11-20: It may be time to shape up.
21-30: Perhaps you think you are still in your 30s?
31-40: You know where you are in life, and enjoy it.