Sitting at your desk from nine to five without exercise could raise the risk of early death by more than half. Credit:Lyn Osborn Current public health advice recommends just half this level of activity - yet almost half of women and one third of men fail to achieve even this. Prof Ulf Ekelund, the lead scientist, from Cambridge University and the Norwegian School of Sports Sciences, said: "We found that at least one hour of physical activity per day, for example brisk walking or cycling, eliminates the association between sitting time and death." He added: "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 your lunchtime, after dinner in the evening. You can split it up over the day but you need to do at least one hour." Researchers said the typical modern routine of spending a day in front of a computer, followed by an evening slumped in front of the television was proving fatal.

They called for radical changes in government policies to encourage healthier habits. These include placing bus stops further apart to force people to walk for longer, closing streets to cars at weekends to encourage more sports and exercise and opening free public gyms in parks. Five-minute breaks Many office workers, especially commuters, would find it hard to avoid long periods of being seated but should make every effort to break up their day, with short walks, the scientists said. "Take a five-minute break every hour, go to the next office, go upstairs to the coffee machine, go to the printer," said Prof Ekelund. "Build physical activity in your everyday life." Dr Pedro Hallal, a fellow researcher, from the Federal University of Pelotas in Brazil, said: "The combination of sitting too much all day, and too little activity is deadly."

The combination of sitting too much all day, and too little activity is deadly Workers need to do double the amount of exercise recommended by health officials in the UK, he said. The studies could not pinpoint why long periods of sitting were specifically risky, but the scientists involved said that movement appeared to assist the body's metabolism, while sedentary periods could influence hormones such as leptin, which regulate energy balance. In the study, participants, mostly aged over 45, were classed by their levels of physical activity, from up to five minutes a day to more than an hour and by the amount of time spent seated. This was compared with death rates over a period of up to 18 years among the adults, who came from western Europe, Australia and the United States. Among those who sat for at least eight hours a day and managed less than five minutes' activity, mortality rates were 9.9 per cent.

For those who spent just as long seated, but managed at least an hour's exercise, death rates dropped to 6.2 per cent. Cancer and heart disease were the two most likely causes of death linked to inactivity. When the scientists looked at the television viewing habits of a subgroup of about 500,000 people, they found that watching for more than three hours a day was associated with an increased risk of death in all groups except those who took at least an hour's exercise. Researchers said that globally, more than 5 million deaths a year are linked to physical inactivity - a similar number to lives lost to smoking, and a higher figure than that caused by obesity. Loading Steven Ward, executive editor of UK Active, said: "This report is showing that inactivity kills. When we realised this about smoking we tackled it - we need to do the same about our office culture." Polls of office workers have found that only one in five leave their workplace at lunchtime, while just 3 per cent use the time to visit the gym.

The Telegraph, London