[Here is some good advice on how to counter the problems of sitting. Even moderate, leisurely exercise of 1 hour a day can make a big difference. Jan]

When you sit, you use less energy than you do when you stand or move. Research has linked sitting for long periods of time with a number of health concerns. They include obesity and a cluster of conditions — increased blood pressure, high blood sugar, excess body fat around the waist and abnormal cholesterol levels — that make up metabolic syndrome. Too much sitting overall and prolonged periods of sitting also seem to increase the risk of death from cardiovascular disease and cancer.

Any extended sitting — such as at a desk, behind a wheel or in front of a screen — can be harmful. An analysis of 13 studies of sitting time and activity levels found that those who sat for more than eight hours a day with no physical activity had a risk of dying similar to the risks of dying posed by obesity and smoking. However, unlike some other studies, this analysis of data from more than 1 million people found that 60 to 75 minutes of moderately intense physical activity a day countered the effects of too much sitting. Another study found that sitting time contributed little to mortality for people who were most active.

More study is needed on the effects of sitting and physical activity on health. However, it seems clear that less sitting and more moving overall contribute to better health. You might start by simply standing rather than sitting when you have the chance or finding ways to walk while you work. For example:

• Take a break from sitting every 30 minutes.
• Stand while talking on the phone or watching television.
• If you work at a desk, try a standing desk — or improvise with a high table or counter.
• Walk with your colleagues for meetings rather than sitting in a conference room.
• Position your work surface above a treadmill — with a computer screen and keyboard on a stand or a specialized treadmill-ready vertical desk — so that you can be in motion throughout the day.

The impact of movement — even leisurely movement — can be profound. For starters, you’ll burn more calories. This might lead to weight loss and increased energy. Also, physical activity helps maintain muscle tone, your ability to move and your mental well-being, especially as you age.

Source: https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/sitting/faq-20058005