The human body is remarkable and is capable of some amazing feats. It has been designed to withstand great environmental pressures. For an untold number of generations, the human form has been sculpted by many factors. However, one environmental factor that up until only a generation or two ago has not been present and recent research is showing that our body is not easily adapting to it. This is the advent of the sedentary lifestyle.
Our ancient relatives did not have the luxury of having automobiles, elevators, escalators or moving walkways. They had to walk, jog, skip or run to get from one point to the next. Being in motion was how we evolved, jumpstarting the changes that would one day allow us to walk upright and move more efficiently. To say that the human body is built to move would be an understatement. With people practicing increasingly sedentary lifestyles (either by choice or circumstance, such as when required by work), risks of developing diseases and other health conditions also increase, ranging from the mild (bad posture, neck sprain) to the moderate (chronic back pain) to the severe (conditions relating to the spine and joints, obesity, cardiovascular disease, cancer). In short, while rest and relaxation are necessary for good health, too much hurts.
Already, numerous studies have shown the dangers of leading a sedentary lifestyle, the kind where the majority of one's waking hours is spent seated. In one such study, (Schmid, D., Leitzmann, M.F., Television Viewing and Time Spent Sedentary in Relation to Cancer Risk: A Meta-Analysis, Journal of the National Cancer Institute, 2014) the relationship between features of a sedentary lifestyle (length of TV viewing and length of time spent sitting - both recreational and occupational) and the risk of developing different types of cancers was explored. It included a meta-analysis of over 40 observational studies involving more than 4 million subjects and nearly 70,000 cases of cancer. The researchers found that there was "significantly higher risk" in individuals who spent more time being sedentary of developing cancers of the colon, lungs and endometrial lining. Furthermore, the risks increased for every two-hour increase in the time spent sitting.
In a study headed by Prof. Andrea LaCroix of the University of California, San Diego's Women's Health Center of Excellence, she showed a connection between sitting for long time periods and a higher risk of death among older women. Per LaCroix, too much time spent sitting has been linked to health issues such as heart disease, heart attacks, and even cancer. In the same study, she also found that older female subjects who spent more time being inactive had a higher risk of dying within 12 years following the study.
Although the real reason why sitting is linked so closely to unwanted health issues, conditions and diseases are unclear, there are theories that support the belief that prolonged sitting, as ordinary as it is, could be dangerous. Here are a few of the possible reasons why:
Fewer calories are burned when sitting than when standing up. A 120-lb. individual working in an office for 8 hours, for example, could burn about 220 more calories when working while standing. That translates to more than 1,000 calories in a 5-day work week.
The pancreas is less efficient at producing insulin to regulate the levels of glucose or sugar in the body while it is at rest. The less active a person is, the less efficient the pancreas works.
Heart rate is generally faster when standing up than when sitting down. Thus, blood flows better throughout the body carrying fresh, healthful oxygen to the cells. A team of researchers at the University of Chester in the U.K. noted that volunteers in a study that examined the physiological changes in the body when standing up and sitting down clocked an average of 10 heartbeats a minute more than when they were sitting down. Per the researchers, this is equivalent to burning around 0.7 calories a minute. While it may look insignificant, the difference can add up to nearly 50 calories per hour.
Blood circulation is more sluggish. With poor circulation, the risk of certain health issues increases, including edema in the lower extremities, shortness of breath, skin blemishes, numbness, cramps, and headaches. Poor circulation may also affect the brain's ability to retain information.
Prolonged sitting could increase appetite. In one study (Granados K, Stephens BR, Malin SK, Zderic TW, Hamilton MT, Braun B. Appetite regulation in response to sitting and energy imbalance. Appl Physiol Nutr Metab. 2012 Apr; 37(2):323-33.), a team of researchers observed that sitting longer could encourage people to consume more food, thus increasing their risk of gaining unhealthy weight.
Based on these studies, spending more time on a chair could lead to health problems later, some of which are far more worrisome than simple muscle cramps, pins, and needles on the hands and feet, and the appearance of love handles along the mid-section. Sitting too much and for too long can be dangerous. Spending too much time being inactive can shorten life.