The Impact of Sitting All Day – Part 4 15 May 2020
In part 1, I looked at the impact of sitting on your muscles, and in part 2 generally explored the impact on the rest of your body. In part 3 I focused on the impact of sitting on your circulatory system including your heart. In this article I will explore the impact of sedentary behaviour (sitting) and the link to cancer.
So how common is cancer?
According to Cancer Research UK
Every two minutes someone in the UK is diagnosed with cancer.
1 in 2 people in the UK born after 1960 will be diagnosed with some form of cancer during their lifetime.
Breast, lung, prostate and bowel cancers together account for over half of all new cancers each year.
Overall cancer incidence rates in Great Britain have increased by more than a third since the mid-1970s, with almost this entire rise occurring before the late 1990s.
And here is the good news is more people survive cancer than die from it now.
46% of men and 54% of women cancer patients diagnosed in 2010-2011 in England and Wales are predicted to survive 10 or more years.
Cancer survival in the UK has doubled in the last 40 years.
The Link Between Cancer & Inactivity
Last year in a meta-analysis, Daniela Schmid and Michael F. Leitzmann of the University of Regensburg in Germany analyzed 43 observational studies, amounting to more than 4 million people’s answers to questions about their sitting behavior and cancer incidences. The researchers examined close to 70,000 cancer cases and found that sitting is associated with a 24% increased risk of colon cancer, a 32% increased risk of endometrial cancer, and a 21% increased risk of lung cancer.
D Schmid & MF Leitzmann, 2014, Sedentary behaviour insreases the risk of certain cancers, Journal of National Institute of Cancer, Volume 106, No 7. see http://jnci.oxfordjournals.org/content/106/7/dju206.full
The really bad news is that your can't exercise away the harmful effects, "Adjustment for physical activity did not affect the positive association between sedentary behavior and cancer" write Schmid & Leitzmann. Even participants who achieved the daily recommended levels of physical activity were at the same risk as those who spent their day sitting.
One theory as to why this is the case, is that regular movement boosts natural antioxidants that kill cell-damaging and potentially cancer-causing free radicals, another theory is that the excess insulin encourages cell growth.
The pancreas produces insulin, a hormone that carries glucose to cells for energy. But cells in idle muscles don't respond as readily to insulin, so the pancreas produces more and more. A 2011 study by Stephens et al found a decline in insulin response after just one day of prolonged sitting.
Stephens et al, 2001, Effects of 1 day of inactivity on insulin action in healthy men and women: interaction with energy intake, Metabolism Volume 60, No 7 pages 941 - 949. see http://www.sciencedirect.com/science/article/pii/S002604951000315X