The Times on Saturday: What a sedentary life really does to your health.

Matt shares his advice with Peta Bee 31st January 2015

What a sedentary life really does to your health

Even if you take regular exercise, sitting down for hours increases the risk of heart disease and diabetes. Peta Bee reports

If you squeeze a gym session into your lunch hour or run home from work, you might think you deserve to put your feet up in the evening. Not according to a new science paper that suggests that the benefits of regular exercise can be blunted if you spend the rest of the day sitting down. Dr David Alter, a cardiovascular researcher at the University of Toronto, found that even dedicated gym-goers had a higher risk of heart disease, cancer and early death if they also sat in a chair for several hours daily. In short, you could be training for a triathlon and simultaneously qualify as a couch potato.

Dr Alter says most people don’t realise how much time they spend seated. There’s little doubt that the amount of time we spend in the parked position has increased substantially in recent years. Britain has been labelled one of the most sedentary countries on earth, with almost double the number of “inactive” people as there are in France. We sit down at work, at home and in the car, totting up a staggering average of 8.9 hours a day on our bottoms. In his review of 47 studies on sedentary behaviour, Dr Alter found that the more hours people sat, the higher the number of negative health outcomes. Heavy sitters who were in a chair for seven, eight or nine hours a day showed a 90 per cent greater risk of developing diabetes and an 18 per cent higher chance of dying
from heart disease or cancer than those whose sat less.

Fit people who exercised regularly were not immune; risks rose at the same rate every hour spent seated. “You can make a little bit of headway on the bad effects of sedentary time by at least doing some exercise,” Dr Alter says. “But you can’t completely nullify it.”

What’s shocking is that as little as 60 minutes of sitting can make a dramatic and unwelcome difference to your health. When a group of healthy young men were asked to sit without moving their legs, researchers at the University of Portland reported that “flow-mediated dilation” — the amount arteries were able to expand as a result of increased blood flow — was impaired by as much as 50 per cent after just one hour. Such changes to the arteries are among the first markers of heart disease and a stroke, as arteries might become stiff and less able to pump blood around the body. A five-minute walk every hour was found to offset some of the heart risks but other metabolic effects of staying in your chair are equally as sinister.

Studies on rats have shown that substances that play a crucial role in metabolising fat and sugar in the body are only produced when muscles are being used, even if that’s just standing up. Prolonged sitting has been linked to a sharp reduction in the activity of an important enzyme called lipoprotein lipase that breaks down blood fats and makes them available as a fuel to the muscles, raising the risk of heart disease.

Meanwhile, German researchers showed that the risk of some forms of cancer — bowel, endometrial (womb lining) and lung — rises with every additional two hours you spend in a chair. A US study involving 63,000 middle-aged people showed that four hours in a chair raised the risk of chronic poor health, while those sitting for at least six hours were significantly more likely to have diabetes.

John Brewer, professor of applied sport science at St Mary’s University, Twickenham, says such findings are a cautionary reminder that you may not be as active as you think. “It’s so important to emphasise that an overall active lifestyle is better for your health in the long term than occasional short bursts of exercise,” Brewer says. Prolonged sitting has also been shown to cause sharp spikes in blood sugar levels after meals, creating the perfect physiological setting for type 2 diabetes, Brewer says.

Matt Todman, a physiotherapist with Six Physio, says sitting also has insidious effects on injury risk that might negate the benefits of lengthy warm-ups or that weekly yoga class you attend to improve your posture.

“Sitting for hours on end triggers a domino effect,” says Todman. “The back becomes more mobile, the gluteal muscles don’t work and other muscles like the hamstrings shorten and tighten.” The upshot, he says, is a greater risk of back and shoulder pain as well as strains and pulls when you exercise immediately after a sitting marathon. “The best prevention for back and posture problems is regular movement,” Todman says. “Stand up whenever you can, drink lots of water so that you need to make trips to the bathroom if that’s what it takes to force you to move.”

Dr Alter says standing up every 30 minutes is a good rule, as is taking phone calls on your feet. Don’t think of your workout as an excuse to do little for the rest of your waking hours.

“For most people, exercise really doesn’t take up huge chunks of the day,” Professor Brewer says. “Any physical activity is, of course, beneficial, but it’s not just the gym sessions, the [high intensity] training and the cycling that are helpful. It comes down to minimising sitting as much as we can. However fit we think we are, we all need to spend more time on our feet.”

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