ABSTRACT
Physical inactivity is highly prevalent in most adults not accumulating enough physical activity to meet the recommendations (e.g., 150 min/week of moderate-intensity aerobic activities). At the same time, the majority of adults from developed countries are spending more than two-thirds of their waking hours sitting. Physical inactivity combined with high amounts of sitting time has more severe health consequences than either behavior alone. Therefore, it is now clear that the pandemics of both too much sitting and a physically inactive lifestyle contribute to significant health problems such as cardiometabolic diseases (obesity, type 2 diabetes, and cardiovascular diseases) as well as mental health issues (depression, anxiety, stress, poor sleep). This chapter will introduce the readers to these sedentary and inactive behaviors including their prevalence, determinants, economic costs, and potential biological mechanisms linking their behaviors to the development of non-communicable chronic diseases. We will also discuss the issues surrounding measurement of sedentary behavior and the need for the development of physical activity guidelines that include sedentary time in conjunction with physical activity.
