Today’s guest post comes from Dr Meredith Peddie. You can find more on Meredith at the bottom of the post.
“Sitting is the new Smoking”… we’ve all heard it…. It even made an appearance on Criminal Minds last week (sorry New Zealand TV is probably months out of date)… and yes, there is an ever growing number of studies that indicate that people who sit for long periods are at greater risk of developing, and dying from cardiovascular disease, diabetes and cancer. There are also studies that indicate that people’s pattern of sitting might also affect their risk of diabetes and cardiovascular disease (longer periods of interrupted sitting are worse than short bouts that are regularly interrupted with activity). However, the vast majority of these studies are observational in nature, meaning that they can’t tell us if changing peoples sitting patterns will actually reduce their risk of developing and dying from the above mentioned diseases.
Unfortunately, a study in which you actually changed peoples sitting patterns and then waited to see if that affected whether or not they would develop cancer or cardiovascular disease would take years, and require a large number of people…. So that is where our study comes in… we decided to investigate whether different patterns of activity and sitting would affect risk factors for cardiovascular disease in a very acute setting. Specifically, our study was designed to compare the effects of prolonged uninterrupted sitting, a single continuous bout of physical activity combined with prolonged sitting, and sitting with regular activity breaks on postprandial metabolism.
To do this we conducted a randomized cross over study in which 70 healthy, normal weight men and women participated in three intervention days, one in which they sat continuously for 9 h (except then they had to get up to use the bathroom), one in which they walked briskly uphill on the treadmill for 30 min and then sat for the remainder of the 9 h, and one in which they performed regular activity breaks (1 min and 40 sec walks on the treadmill every half an hour – giving us a total of 30 min on the treadmill over the 9 h) sitting in between each break.
During this time we fed them three times, and collected blood samples at regular intervals for the analysis if glucose, insulin and triglyceride. – Sound familiar? Yes, our study is very similar in design to a study Travis conducted as part of his PhD, and to the study David Dunstan conducted in Australia, however, the key differences are we used healthy, normal weight adults as participants (not children or overweight adults) and had an intervention day which was designed to mimic someone meeting the current physical activity guidelines, but still spending a lot of time sitting.
What did we find?
Regular activity breaks resulted in a 39% reduction in plasma glucose, and a 26% reduction in plasma insulin when compared to prolonged sitting. But what was surprising was that we also found a 37% reduction in plasma glucose and an 18% reduction in plasma insulin when regular activity breaks were compared to 30 min of physical activity combined with prolonged sitting. Obviously sitting for long periods isn’t that great for glycemic control! What was also surprising to us was that neither physical activity, nor regular activity breaks resulted in plasma triglycerides being difference from prolonged sitting. This was particularly surprising because one of the highly publicized biological mechanisms proposed to explain the link between sitting and poor health is the activation of an enzyme called lipoprotein lipase, which is involved in clearing triglycerides (the fat that appears in the bloods after a meal) out of the bloodstream.
What is the take home message?
Obviously there are well established benefits of participating in structured, longer bouts of physical activity on a regular basis, and we don’t want this research to distract from that, or discourage people from trying to fit at least 30 min of physical activity into their lives on most days of the week…. However, this research does suggest that regularly breaking up periods of prolonged sitting could also be a very important thing to do for your health. So if you’ve been sitting at your computer reading this… maybe its time you got up and walked around, it doesn’t have to be for long… about a 1 min 40 sec should do it.
About the author: Meredith Peddie is a Heart Foundation Research Fellow in the Department of Human Nutrition at the University of Otago, Dunedin , New Zealand. Her research focuses on the health benefits of breaking up sitting time with regular activity breaks, with a particular focus on carbohydrate and fat metabolism. You can find out more on Dr Peddie at her University of Otago profile page.