At least an hour of physical activity a day may be required to offset the harmful effects of sitting at a desk for eight hours, according to the latest study to highlight the perils of a sedentary lifestyle.
The World Health Organisation (WHO) guideline, adopted by Public Health England, recommends 150 minutes of exercise a week but research, based on data from more than one million people, suggests that is insufficient for many.
A team of international experts found that the risk of dying during a follow-up period of two to 18 years was 9.9% for those who sat for eight or more hours a day and engaged in low activity, compared with 6.8% for those who sat for less than four hours a day and were active for at least one hour a day.
But they also found that the increased risk of death associated with sitting for eight hours a day was eliminated for people who did a minimum of one hour of physical activity a day.
Lead author Prof Ulf Ekelund, from the Norwegian School of Sports Sciences and Cambridge University, said: “You don’t need to do sport, you don’t need to go to the gym. It’s OK doing some brisk walking, maybe in the morning, during lunchtime, after dinner in the evening. You can split it up over the day, but you need to do at least one hour.”
The paper, published in the Lancet on Wednesday, analysed data from 16 previous studies, mainly involving people aged over 45 from the USA, western Europe and Australia. The authors found that one hour of “moderate intensity” exercise, such as walking at 5.6 km/h or cycling for pleasure at 16 km/h, was enough to offset the ill effects of sitting for long periods.
Ekelund acknowledged that work pressures made taking lengthy breaks – the legal minimum in the UK is one 20-minute break – unrealistic for some.
“It’s not easy to do one hour of physical activity a day but … the average TV viewing time in adults in the UK today is 3hrs 6mins or something like that, more than three hours,” he said. “I don’t know if it’s too much to ask that just a little bit of those three hours may be devoted to physical activity.”
Ekelund also said a five-minute break at work every hour, even to go to the printer, would be beneficial and said it was in employers’ interests to facilitate culture change.
Another study, published in the Lancet on Wednesday as part of the same series, estimates that physical inactivity costs the global economy $67.5bn (£51.5bn) per year – the UK equivalent is £1.7bn – comprising $58.8bn in healthcare and $13.7bn in lost productivity.
Independent experts who reviewed Ekelund and team’s research said it was encouraging that it suggested sedentary time could be mitigated. Dr Erika Borkoles, senior lecturer in sports science at Bournemouth University, said: “People who sit for longer hours should be concerned and could take the findings of this research as an opportunity to be proactive.”
A WHO spokesman said: “Recommendations related to sitting and sedentary behaviours are not available yet. However, WHO already recommends governments implement policy actions around making environments where people live and work more conducive to physical activity.”
PHE said even 10-minute bursts of activity could be beneficial.
Ekelund and his team found that sitting watching TV for over three hours per day was also associated with an increased risk of death during the follow-up period, except among the most active.
The increased risk was slightly greater than that associated with total sitting time, possibly because TV watching may indicate a more unhealthy lifestyle in general, including being less likely to take exercise. People may also snack unhealthily while viewing.
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