Your Mum is right - Don't sit all day!

StephenW

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Sitting nine to five (and beyond): the perils of sedentary lifestyles

David Dunstan, The Conversation

Friday, 12 August 2011

Whether it’s at work, in cars, watching TV or using the computer, there’s no denying many of us spend the majority of our days sitting. And while science is yet to prove conclusively that too much sitting is deadly, the associations between inactivity and the risk of chronic illness, such as diabetes and heart disease, are of significant concern. Last year, we published a six-year study that found every hour spent watching television (which usually involves sitting) increased the participant’s risk of death from chronic disease by 11 per cent. How much exercise do we need? It’s widely accepted that for good health we should get 30 minutes of exercise a day on most days of the week. But this may not be enough if the rest of our time is spent sitting. It’s only in recent years that we’ve recognised the importance of adopting a whole-of-day approach to examine levels of physical activity (and inactivity) and how it affects health. Sitting down for prolonged periods without a break can slow the body’s processing of fats, glucose and other substances. This increases the risk of developing chronic disease, even for people who adhere to the national physical activity recommendations. The absence of movement can also slow down our metabolic processes. And when we’re sitting down, our skeletal muscles, particularly in the lower limbs are not active. When our muscles are prevented from contracting for prolonged periods, the body’s regulatory processes – such as the circulation and burning of glucose – are compromised. Our research has shown that even when people exercise regularly, watching large amounts of television is independently associated with an increased risk of premature death. International research backs this up, including a study from the American Cancer Society which found that time spent sitting was independently associated with a greater risk of death – particularly of heart disease ––regardless of physical activity level. But we must be careful not to draw conclusions too quickly. A United Kingdom study published this year in the Annals of Internal Medicine found that working more than 11 hours a day increases your risk of heart disease by 67 per cent, compared with those working standard seven- to eight-hour days. With this type of study, it’s important to consider the many factors that may alter the result, including: the participants' exposure to food of low nutritional value, whether they worked in shifts (evidence shows shift workers are more susceptible to adverse health outcomes mainly as a result of disruption to the body’s normal processes), whether the participants smoked, and the stressfulness of their job, just to name a few. It wouldn’t be surprising that a person who spends an extra few hours a day in a stressful environment would have a greater risk of heart disease. So how much sitting is too much? My research team at Baker IDI is developing some of the first definitive information about the links between sitting time of office workers and metabolic health. We’re hopeful our research will form the basis for the development of recommendations to reduce Australians' health risks from too much sitting. In the meantime, alarm bells should be ringing for many office workers who spend a large part of their day sitting. But it’s not all bad news – we can improve our health simply by standing up and moving around every 20 to 30 minutes.