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This month, three studies show that prolonged sitting is associated with increased risk for heart attacks and cancer.
Heart Attacks: The Women's Health Initiative study shows that sitting for 10 hours per day increases a woman's chances of suffering a heart attack by 20 percent when compared to sitting for five hours per day (Journal of the American College of Cardiology, April 19, 2013, published online ahead of print). Those who sat for 10 hours per day and also had no exercise program had a 70 percent increased risk. Being overweight further increased their chances of having a heart attack.
Cancer: The Southern Community Cohort Study showed that, compared to sitting less than 5.5 hours per day, sitting for 12 or more hours per day almost doubled breast cancer risk in white (but not black) women, (Cancer Prevention Research, April 13, 2013).
Survival from Cancer: Being overweight and not exercising increased risk for heart attacks, and disability in breast cancer survivors after treatment (Anticancer Research, April 2013; 33(4):1595-1602).
Why Prolonged Sitting Increases Attack Risk
A high rise in blood sugar after meals markedly increases risk for a heart attack and moving your muscles in any way helps to prevent blood sugar levels from rising too high. Every cell in your body is like a balloon full of fluid. A high rise in blood sugar causes sugar to stick to the outer surface of cell membranes. Once stuck there, sugar can never get off and is eventually converted to sorbitol which destroys the cell. This sticking of sugar on cell membranes damages the inner lining of arteries and is part of the process of forming plaques in arteries. You can have damaging high rises in blood sugar even if you are not diabetic.
Contracting Muscles Lower Blood Sugar Levels
Resting muscles remove virtually no sugar from the bloodstream. However, contracting muscles remove sugar from the bloodstream at a rapid rate and don't even need insulin to do this. This effect is maximal during vigorous exercise and continues at a high level for up to an hour after you finish and then tapers off to almost no effect after about 17 hours.
To prevent high rises in blood sugar, you need to keep contracting your muscles. People who sit around all day long can expect to have higher blood sugar levels after they eat. Other factors that raise blood sugar levels include:
Being overweight. Fat blocks insulin receptors.
Eating or drinking sugars and refined carbohydrates: all sugared drinks, all foods with added sugars, and foods made from flour such as bakery products and pastas.
Eating red meat (saturated fat in red meat blocks insulin receptors).