PHYSICAL ACTIVITY AND OBESITY by Claude Bouchard, Peter Katzmarzyk

Physical activity measures often reflect what type of activity people are doing (mode or type); how long they perform an activity in minutes or hours (duration); how often they do the activity in days, months, or years (frequency); and how hard the activity feels or how much the activity increases the resting metabolic rate (intensity). Intensity is measured in terms of METs, shorthand for metabolic equivalents. One MET reflects the kilocalorie energy requirement of sitting quietly in a chair. 0 METs) (4).

The change in lipoprotein lipase was more pronounced in response to an experimentally induced increase in sedentary behavior when compared to the addition of vigorous exercise training to normal activity levels. Behavior Compensation The emerging evidence that sedentary behavior has independent effects on health and may also mediate the relationship between physical activity behavior and health elevates the importance of carefully assessing whether the introduction of one behavior affects the other.

However, individuals can achieve high levels of both physical activity and sedentary behaviors, and one type of behavior does not automatically displace the other. Evidence suggests that sedentarism has independent effects on obesity and health and consequently should be treated as a separate and distinct construct (2-5). For the purpose of this chapter, sedentarism is defined as purposeful and extended engagement in behaviors characterized by minimal movement, low energy expenditure, and rest.