Are you sitting comfortably? Bad idea. Stand up and walk around the house. Leave your desk and jog down the office stairs. Even better – jog up the stairs. If it’s lunchtime, go and join a yoga class or head for the shops on foot. What’s to lose? You are going to feel better and live longer.

Hardly a day goes by without a new piece of research flagging up the benefits to our physical and mental health of getting more active. On Tuesday, a study of 30,000 Norwegians by the brilliantly named Black Dog Institute in Australia found that even one or two hours’ exercise a week can help prevent depression. On Monday, the Wildlife Trust revealed that two-thirds of its volunteers, digging ditches and building bird tables in the open air, had better mental health within six weeks.

Getting off your backside and moving about, preferably a bit vigorously some of the time, will stave off heart disease, strokes, cancer and diabetes. It can keep your blood pressure steady and helps you sleep. You may not shed pounds, but it will help keep your weight stable. It can overcome anxiety and boost self-esteem. Older people who are active are less likely to have a hip fracture or a fall.

We have the sitting disease. According to a report by Public Health England (PHE) in March, physical inactivity is one of the top 10 causes of disease and disability in England. It is responsible for one in six deaths in the UK, which is the same as smoking. It costs the UK an estimated £7.4bn a year.

If exercise was a pill, it would be the biggest blockbuster in the history of medicine.

We weren’t built to sit in front of a computer, a TV screen and a steering wheel. We were designed to be moving around.

“It is what we were made to do,” says Nick Cavill of Oxford University’s department of public health. “Everyone probably knows the basic point, but often we overlook it in our busy modern lives. We are hunter-gatherers. We were designed to be physically active all day long.

“Our bodies are still stuck in neolithic times, while our minds are in the 21st century.”

I don’t care how you get hot and sweaty for 10 minutes each day. I just want you doing it

Given our ancestors were chasing dinner all day long, you might think it follows that we need to be physically active the entire time we are awake, jogging on the spot at our standing desk. But, thankfully, Cavill says no. Long-term studies, following active and sedentary people until their deaths, have worked out that there is a dose-response curve.

“The more exercise you do, the better it is – up to a certain level,” he says. “A marathon runner or a triathlete is not doing much better for their health than somebody who is reasonably active. Half an hour a day is what they say now – or two for the price of one if you do vigorous exercise. Every vigorous minute is the equivalent of two moderately active minutes.”

Dame Sally Davies, England’s chief medical officer who practises before she preaches, goes for a jog twice a week – even though she says she doesn’t much like it – in order to set an example. She advocates 150 minutes of physical activity a week, which is the equivalent of half an hour, five days a week. That can be walking or cycling. It should be enough to raise your heart rate, make you breathe faster and feel warmer. Vigorous activity is something that makes you out of breath.

The fashion these days is not for gym membership but better lifestyles. Phone apps that tell us how many steps we have walked each day have been revelatory. An obsession, in some cases. Cycling and strolling, walking up escalators and shunning lifts, standing up every 20 or 30 minutes (there are those who set their phones or timers) are all healthy. But there is also the “forgotten recommendation”, says Cavill, which is a bit harder to incorporate into the way we live today. We should all be doing some load-bearing exercise. According to NHS Choices, adults should be doing exercises on two or more days a week “that work all the major muscles (legs, hips, back, abdomen, chest, shoulders and arms)”.

This is particularly important for women as they age, to avoid the weakening arm muscles and bone thinning that can lead to fractures. And we don’t routinely lift loads much any more. “Internet shopping is bad for you,” remarks Cavill. The answer is “anything you can think of that uses muscles” – either that walk back from the local shops carrying bags of groceries or boring bicep curls and sit-ups, perhaps with weights. Or digging in the garden, or yoga.

Cavill thinks there may be a particular benefit from activities undertaken outdoors. “I certainly feel it myself. I’d much rather exercise in the woods than in the gym,” he says. Conservation projects and “green gyms” do well. It is back to the hunter-gatherer point. We were not made to live inside.

Load-bearing exercises such as press-ups are particularly important for women. Photograph: Alamy

Dr Justin Varney, the adult health and physical activity lead at PHE, likes to talk about “physical activity”. He says the word “exercise” conjures for most of us “Lycra and exercise cycles, and although that works for some people, for others it’s like saying: ‘Let’s go and climb Mount Everest tomorrow.’”

PHE encourages brisk walking, gardening, dancing – anything physical, really. “I don’t care how you get hot and sweaty for 10 minutes each day. I just want you doing it,” he says.

He doesn’t expect or even want everybody to get their 150 minutes a week by doing the same activity every day. That’s not the way we are. “We are by nature promiscuous with our physical activity and that’s great,” he says. It will make a huge difference not only to how well you live, but how long you live. “Whether you can get out of a chair on your own is one of the best predictors of premature mortality as you age,” he says.

It is so important to be active – and yet none of the experts any longer thinks it is enough just to tell people that. As with unhealthy eating and drinking too much, we enjoy sitting about too much to want to stop. To make us move, physical activity has to be almost impossible to avoid. A ban on cars is not likely any time soon. But efforts are under way to steer us towards shanks’s pony instead by redesigning our towns and cities. Or, more realistically, tweaking them when the opportunity arises. That means, for instance, painting cycle routes on roads where it isn’t feasible to put in a protected lane.

In March, a report by PHE opened with the gloomy news that half of all women and one in three men are still damaging their health by sitting around. “The decline in activity seen since the 1960s will put increasing pressure on strained health and social care, and the quality of life for individuals and communities, unless addressed,” it said. It was an update on a report called Everybody Active, Every Day, which came out in October 2014. It takes years to shift people’s habits, it reflected, but the efforts in two years had seen a 1% increase in the numbers of people doing their 150 minutes a week – or half a million people in England enjoying better health and wellbeing.

Like cutting down on junk food, it has been recognised that we need some help – that the environment around us, full of cars and snacks, elevators and sugary drinks, is a part of the problem that governments not only could but should do something about, from ensuring we have green spaces to walk in to prioritising pedestrians and cyclists when it comes to designing new traffic systems.

Varney has just been working with the World Health Organization on a new global action plan for physical activity. “It’s about what member states can do to make it easier for their people. At the end of the day, people make decisions in their lives based on what is easiest, most effective and most efficient, or what gives them most joy. If you go out of your front door and there is no place to walk or it’s not safely lit, you are not going to do it.”

He is hugely enthusiastic. He talks about increasing sports and physical activity in schools and ensuring doctors and nurses get taught about the importance of physical activity – and that it is part of their exams so they revise.

It is a huge undertaking to change our culture to make us more active, even though it will make us all healthier and happier. These initiatives are not drops in the ocean, says Varney. He prefers to think of them as a bunch of pebbles. “You throw them into a pond so that the ripples become a wave and the waves change the shoreline.”

They get it right in Amsterdam and in Copenhagen, of course, where everybody seems to be born on two wheels, and apparently also in Finland. “There is a strong exercise culture, perhaps rooted in cross-country skiing and outdoor exploration,” says Cavill. “They do Nordic walking in the summer. Legally and policy-wise, they have pushed it for years. Someone told me the Finns are very obedient. If the government tells them to exercise, they exercise.”

The British are not usually characterised that way. But if we all understood that happiness and health is just a light jog away, maybe we would vote with our feet.

How much exercise should we be doing?

One minute of vigorous activity is worth two of moderate effort. Photograph: Alamy

The key to a healthy body and mind is a combination of aerobic and strength exercises several times a week, explains Dr David Broom, a senior lecturer in physical activity and health at Sheffield Hallam University. “Variety is the spice of life and we should be doing a different range of physical activity so we don’t get bored. It is also about reducing sedentary behaviour and getting up and moving around every 20 minutes.”

0 to five-year-olds

Babies and toddlers need to be active throughout the day, every day, to enable them to develop gross motor skills and physical literacy. This can involve a variety of movements:

- Reaching and grasping, pulling and pushing

- Lying on their stomach and lifting their body up, also known as “tummy time”

- Toddlers should be active for at least three hours a day with a mixture of light play, such as walking and moving around, and energetic play, such as running or climbing

Five to 18-year-olds

Developing bone strength is crucial for young people, as they reach their maximum bone density between the age of 18 and 20.

- Youngsters should be moderately or vigorously active for at least an hour a day, and on three days a week this should involve strengthening activities such as skipping, jumping, running and gymnastics

- Moderate aerobic activities could include walking, riding a scooter, skateboarding or cycling

- Vigorous activities include running, swimming, martial arts, rugby and dance

19 to 64-year-olds

The main focus in this age group is aerobic activity to reduce the risk of disease and premature death, and strength training to support “activities of daily living” such as carrying heavy shopping bags.

- The minimum recommended exercise length is 150 minutes of moderate aerobic activity a week (brisk walking, water aerobics, tennis doubles) or 75 minutes of vigorous activity (running, hockey, uphill cycling), or a mixture of both.

- Moderate or vigorous activity should be complemented with strength exercises at least twice a week, such as heavy gardening, lifting weights or yoga

- The more activity you do and the higher the intensity, the greater the benefit

65-plus

Activities to improve balance, coordination and flexibility are extremely important for older adults so they are able to avoid falls and maintain a good quality of life.

- Older adults are also advised to exercise moderately for at least 150 minutes a week, or do 75 minutes’ vigorous activity

- Weight-bearing activities are more significant at this age so people are able, for example, to get out of a chair unaided and live independently

- There are no restrictions on the types of activities older people should do, and they should continue to do the exercise or sport they enjoy

Lily Canter