Sedentary behaviour or “sitting time” is dangerous for you, even if you are physically active

English: TV icon
English: TV icon (Photo credit: Wikipedia)

More and more studies are showing that being inactive is bad for your health, regardless of the amount of physical exercise you do.

Last May, Ei Ei Nang and colleagues published an article in the International Journal of Behavioral Nutrition and Physical Activity, showing that watching television for longer periods of time puts you at a higher risk of cardiovascular disease and diabetes, even if you are otherwise physically active. They could not show the same increased risk for time spent working on a computer or reading.

Being inactive is different from not doing any physical activity

For more than a decade now, scientists have studied how inactivity affects your health. During some of your daily activities, such as TV watching or driving a car, you consume hardly more energy than while sleeping. Scientists have noticed that if you do so for longer periods of time without interruption –typical TV watching-, your cholesterol and triglycerides levels worsen, your blood pressure increases and your cells become less sensitive to insulin. As this is true even if you work out vigorously on a regular basis, they suspect that inactivity affects your health via different mechanisms than physical exercise.

If so, inactivity for a long period is an independent risk factor, just as smoking, a bad diet or a lack of moderate to vigorous exercise. In other words: what you do between your workouts matters, even if you exercise every day.

How can inactivity affect your health?

Ei Ei Nang and colleagues’ statistical analysis showed that the higher BMI and the lower amount of fibre in the diet of the TV watchers could explain a large part of the increased risk. This confirms other studies which have indeed suggested that TV watching is associated with bad eating habits and snacking.

Marc Hamilton however, has shown that contractions of large muscle groups, even if they are only gentle, are essential for the production of lipoprotein lipase, a protein important for controlling blood triglyceride levels, cholesterol and other risk factors for cardiovascular disease.  If you remain inactive for an extended period of time, your lipoprotein lipase production drops, and your cholesterol and triglyceride levels deteriorate.

Even though you will increase your lipoprotein lipase activity during your workout, it cannot compensate for all the lost time. This explains why the effects of inactivity are independent of the effects of moderate or vigorous exercise.

Marc Hamilton’s theory also explains why working on a computer is less dangerous: the whole body movements office workers have to make on a regular basis might be just enough to stimulate lipoprotein lipase production.

It is of course possible that the increased risk is due to the combination of bad eating habits and a lack of lipoprotein lipase.

What can I do?Strolling in a scenic or tranquil location is ...

If Marc Hamilton is right, you could keep yourself safe by interrupting long periods of inactivity by some gentle whole body movements: strolling at less than 1mph, standing up on a regular basis….Remember that it is not about exercise –you will do that during your workout- but about stimulating lipoprotein lipase production by muscular contractions.

We do not know yet how much we have to move or how often, but as diabetes and cardiovascular disease are so widespread, we should act now.

At the University of Maastricht, Geert Rutten has introduced STUFF (stand up for fitness) to his students: during lectures everybody stands up for at least 5’ every 30’. Initially it felt strange, but after a while it was well accepted.

If you have a better idea, please share it; if not, try it out, and let me know what you think!


Hamilton MT, Hamilton DG and Zderic TW. Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Diabetes 2007; 56(11): 2655-67.

Nang EE, Salim A, Wu Y, Tai ES, Lee J and Van Dam RM. Television screen time, but not computer use and reading time, is associated with cardio-metabolic biomarkers in a multiethnic Asian population: a cross-sectional study. Int J Beh Nutr Phys Act 2013, 10:70 doi:10.1186/1479-5868-10-70.

Rutten GM, Savelberg HH, Biddle SJ and Kremers SP. Interrupting long periods of sitting: good STUFF. Int J Behav Nutr Phys Act 2013; 10:1. doi: 10.1186/1479-5868-10-1.


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