Sitting can be hazardous to your health

Joel McCullough, MD, MPH, MS
Public Health Director and Health Officer
Spokane Regional Health District

Many of us sit a lot at work, in the car, and at home on the couch. That’s probably true for a lot of regular exercisers, including me. I used to think that exercising for an hour or more a day would negate all that sitting. Now a growing body of scientific evidence says that may not be true. That’s a little disheartening, but it’s also a wake-up call for everyone with an office job, even avid exercisers.

An emerging field that some call inactivity studies is challenging long-held beliefs about human health and the role of sedentary lifestyles. We’ve been told for decades how much exercise we should get daily or weekly, with most recommendations now saying at least 150 minutes of moderate-intensity exercise per week or an average of 30 minutes for five days. If it’s vigorous, it can be less. Now the latest research shows that even people who do significant and regular exercise still increase their risk of serious illness from hours of physical inactivity.

The American College of Sports Medicine (ACSM) just came out with new recommendations on the quantity and quality of exercise for adults. The recommendations are not surprising: everyone needs a balanced program of cardiovascular, resistance (strength) exercise, flexibility, and neuromuscular or functional fitness training (balance, agility, coordination). But the ACSM further notes that sedentary behavior (sitting for long periods of time) has been shown to be a health risk by itself. Meeting the guidelines for physical activity does not make up for a sedentary lifestyle.

This is not a new concept. In the 1950’s, researchers found that London’s double-decker bus drivers were more likely to die from cardiovascular disease than bus conductors, and that government clerks were more likely to die than mail carriers. In both cases, the more sedentary job carried greater health risks than the more active job, even though they were in a similar line of work and of similar social and economic class.

Recent research has confirmed this finding. In a study by the American Cancer Society, men who spent six hours or more per day of their leisure time sitting had an overall death rate that was about 20 percent higher than the men who sat for three hours or less. The death rate for women who sat for more than six hours a day was about 40 percent higher. Another study found that for each additional hour of television viewing per day, the risk of dying rose 11 percent. These results remained after taking into account age, sex, education, smoking status, hypertension, BMI, glucose tolerance status, and leisure-time exercise.

Does this make sense physiologically? Consider what happens to your body in a chair: Electrical activity in the muscle drops, leading to a cascade of potentially harmful metabolic effects. Your calorie-burning rate immediately plunges to about a third of what it would be if you got up and walked. The enzymes responsible for breaking down lipids and triglycerides (called lipase) plunge, which in turns causes the levels of good (HDL) cholesterol to fall.  The metabolic changes can also occur in a relatively short amount of time. In young, fit, and thin volunteers, researchers recorded a 40 percent reduction in insulin’s effectiveness in modulating the update glucose in the subjects—after 24 hours of being sedentary. Over a lifetime, the unhealthful effects of sitting can add up.

 

The good news is that the perils of inactivity can be countered. It is possible to reap major benefits through thousands of minor movements each day, through a concept coined NEAT, which stands for Non-Exercise Activity Thermogenesis (thermogenesis is heat energy produced by the body and is an indicator of calories burned). In the world of NEAT, even the smallest movement matters.

NEAT is the energy expended for everything we do that is not sleeping, eating or sports-like exercise.  It accounts for the vast majority of an individual’s non-resting energy needs and includes the energy expenditure of work, leisure, sitting, standing, walking, talking, toe-tapping, playing guitar, dancing, and shopping . NEAT, even in avid exercisers, is the predominant component of activity thermogenesis, and it is the most variable component of energy expenditure. Further research could show it to be a critical component in how we maintain our body weight and/or develop obesity or lose weight.  An illustration of this variability, a motion tracking study found that obese subjects averaged only 1,500 daily movements and nearly 600 minutes of sitting. This compares to farm workers who average 5,000 daily movements and only 300 minutes of sitting.

Think of the many ways you can become more active. If you can perform a behavior while sitting or standing, choose standing. You can also limit your chair time by taking breaks to stand and walk around. If possible, you can stand while talking on the phone or even watching TV. The average person can burn an extra 60 calories an hour just by standing.

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