If you want to stay healthy stand up, warn researchers. In recent years, a growing body of research1 has analyzed sitting time in relation to health. Physical inactivity has been linked with diabetes, obesity, and cardiovascular disease, but it can also increase the risk of certain cancers, according to a study2 published June 16 in the JNCI: Journal of the National Cancer Institute. The study found an additional two hours a day of sedentary behaviour was linked to an 8 percent increased risk for colon cancer, a 10 percent increased risk for endometrial cancer and a 6 percent increased risk for lung cancer. The reason is not clear, but one theory is that excess insulin encourages cell growth.

image of 2people sitting

Muscles burn less fat and blood flows more sluggishly during a long sit, allowing fatty acids to more easily clog the heart. Prolonged sitting has been linked to high blood pressure and high cholesterol, and people with the most sitting time are more than twice likely to have cardiovascular disease than those who are active.

Sitting could lead to the muscle degeneration. It affects our neck, back and the legs. We do not have to use many muscles when we’re sitting down. When we slouch in a chair, abdominal muscles that keep us upright, go unused. Weak abs and tight back muscles can amplify the spine’s natural arch, a condition called hyperlordosis, or swayback.

What’s more, the long sitting could lead to a more rigid spine and disk damage. When we move around, the discs between vertebrae expand and contract, soaking up fresh blood and nutrients. But when we sit for a long time, discs are squashed unevenly and collagen hardens around supporting tendons and ligaments. The pressure within discs is greater when sitting and people who sit more are at greater risk for herniated lumbar disks.

Prolonged sitting affects our upper spine and neck, as well as our hips. As most sitting occurs at a desk at work, holding the neck forward toward a keyboard or tilting the head to cradle a phone while typing, can strain the cervical vertebrae and lead to permanent muscle imbalances. Additionally, when we sit for a long time the hip flexor muscles become short and tight, limiting range of motion and stride length. Sitting make our gluteus muscles (bottom muscles) do nothing, which affects body stability, ability to push off and the ability to maintain a powerful stride.

Sitting for long periods of time slows blood circulation, which causes fluid to pool in the legs. Problems range from swollen ankles and varicose veins to dangerous blood clots called deep vein thrombosis (DVT). Long flights can have a similar effect. Weight-bearing activities such as walking and running stimulate hip and lower-body bones to grow thicker, denser and stronger. Scientists partially attribute the recent surge in cases of osteoporosis to lack of activity.

Moving muscles pump fresh blood and oxygen through the brain and trigger the release of all sorts of brain- and mood-enhancing chemicals. When we are sedentary for a long time, everything slows down, including our brain function.

However, the strongest associations in the analysis were between prolonged sitting and diabetes. There is evidence that being sedentary negatively affects glucose levels and increases insulin resistance – but scientists do not yet know how. “When we sit for long periods of time, enzyme changes occur in our muscles that can lead to increased blood sugar levels, the effects of sitting on glucose happen very quickly, which is why regular exercise won’t fully protect you”3, says lead study author Emma Wilmot, MD.

The message is to reduce our sitting time by breaking it up and add in more standing or walking where possible. Although experts aren’t sure how often we need to get up, they suggest getting up about every 30 minutes if possible. It is also important to sit less outside of work. The average adult sits for 90% of their leisure time, so it is very important to find a healthy balance between sitting, standing and walking or other physical activities.

1 http://jnci.oxfordjournals.org/search?fulltext=sitting&submit=yes&x=15&y=11

2 http://jnci.oxfordjournals.org/content/106/7/dju135.full.pdf+html?sid=63cd5411-4ad3-46c6-97bd-0f4acd394978

3 Wimot EG, Edwardson CL, Achana FA, et al. Sedentary time in adults and the association with diabetes, cardiovascular disease and death: Systematic review and meta-analysis. Diabetologia 2012; 55:2895-2905.