How much do you need to exercise to offset sitting all day?

There has been a lot of attention given to the health risks associated with sitting at a desk all day, or binge-watching TV shows, lately. Now research on over one million people has found that sitting for at least eight hours a day could increase the risk of premature death by up to 60 per cent.

However, according to the Lancet study, an hour of moderate activity a day wipes out the negative impacts of sedentary behavior. This is contrary to some prior studies claiming exercise didn’t help at all.

The authors urged anyone spending hours at their desk to take a five-minute break every hour, as well as exercise at lunchtimes and evenings. They said sedentary lifestyles were now posing as great a threat to public health as smoking, and were causing more deaths than obesity.

An hour of brisk walking or cycling – even spread over a day - was enough to combat the dangers of eight hours sitting in the office, they said.

The study was part of a four-paper series published in the Lancet and launched in London ahead of the Summer Olympic Games. The authors warn there has been too little progress in tackling the global pandemic of physical inactivity since the 2012 Olympics, with a quarter of adults worldwide still failing to meet current recommendations on physical activity.

"Our message is a positive one," said lead author Ulf Ekelund, of the Norwegian School of Sports Science and the University of Cambridge. "It is possible to reduce, or even eliminate, these risks if we are active enough, even without having to take up sports or go to the gym," he said in a statement.

A decent walk – at a speed of just over three miles an hour - was enough to achieve the benefit, he stressed.

“You don’t need to do sport, you don’t need to go to the gym, it’s okay doing some brisk walking maybe in the morning, during your lunchtime, after dinner in the evening. You can split it up over the day but you need to do at least one hour,” he said.

The researchers said the typical modern lifestyle of spending a day in front of a computer, followed by an evening slumped in front of the television was proving fatal.

But those who spent just as long seated, but managed at least an hour’s exercise, saw death rates drop to 6.2 per cent.

Cancer and heart disease were the two most likely causes of death linked to inactivity.

Similar results were found when the scientists looked at the television viewing habits of a subgroup of about 500,000 people. Watching TV for more than three hours per day was associated with an increased risk of death in all groups except those who managed at least an hour’s exercise.

As for those who might protest that an hour a day of exercise isn’t a reasonable expectation for busy people, Ekelund pointed out that the average amount of time adults in the UK spend watching TV is 3 hours and 6 minutes.

“I don’t know if it’s too much to ask that maybe a little of those three hours be devoted to physical activity,” he said. The general rule of thumb, as Ekelund advised: “Sit less and move more, and the more the better.”

The researchers also called for radical changes in government policies to encourage healthier habits.

The series, involving 16 studies, is a follow-up to a 2012 series in the Lancet declaring physical inactivity a “global pandemic,” and estimating that 5.3 million people die each year due to inactivity.

Earlier this year, Ireland launched its first National Physical Activity Plan, with the aim of increasing the number of people taking regular exercise by 50,000 a year over the next decade. Seven out of 10 adults are too inactive and fail to get the necessary 30 minutes a day of moderate activity five days a week, which is recommended for 18- to 64-year-olds.