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Inactivity is defined as doing less physical activity (PA) than the recommended levels. In 2021, the recommendation for children and youth aged 5–17 was to do at least 60 minutes of moderate‐ to vigorous‐intensity PA daily, preferably aerobic and performed as play. For adults, the 2021 recommendations call for at least 150 minutes of moderate‐intensity aerobic PA per week, or at least 75 minutes of vigorous‐intensity aerobic PA throughout the week, or an equivalent combination of moderate‐ and vigorous‐intensity activity.

More than one in four adults globally (~1.5 billion people) were physically inactive in 2018. Women were less active than men (32% men were active vs. 23% women). Citizens from high‐income countries were more inactive (37%) compared with citizens from middle‐income and low‐income countries (16%). Older adults were less active than younger adults (Figures 3.1 and 3.2a and b).

Regarding the pediatric population, 81% of adolescents aged 11–17 years did not meet physical activity recommendations in 2010. Adolescents from the Southeast Asia region showed the lowest prevalence of insufficient PA (74%), whereas the highest were observed in the Asian Pacific region, the Eastern Mediterranean region, and the Sub‐Saharan African region (92%, 89%, and 85%, respectively). Globally, adolescent girls were generally less active than adolescent boys, with 85% vs. 78% not meeting WHO recommendations. Furthermore, the prevalence of inactivity was highest in the upper‐middle‐income countries and lowest in the lower‐middle‐income countries, for all age groups.

The high prevalence of physical inactivity globally is attributed to insufficient participation in PA during leisure time and an increase in sedentary behavior during occupational, domestic, and transportation activities. Research into the correlates (i.e., factors associated with activity) or determinants (i.e., those with a causal relationship) has proliferated in the past two decades, mostly focused on individual‐level factors in high‐income countries, and has shown that age, sex, health status, self‐esteem, and motivation are associated with PA. However, recently developed ecological models suggest that various components of the social and physical environment, e.g., urban planning, transportation systems, parks, and trails, significantly affect our daily physical activity.

Modern urbanization has resulted in environmental changes that are thought to discourage participation in PA in all domains, such as an increase in violence, high‐density traffic, and air pollution, as well as a lack of parks, sidewalks, and sports/recreation facilities. The aforementioned factors might explain, at least in part, the lower prevalence of physical inactivity in low‐ and lower‐middle‐income countries, due to maintenance of work and transport‐related PA, and the higher prevalence observed in higher‐income countries, where the increased automation of life creates opportunities for sedentariness.

Inactive adults have 20–30% increased risk of all‐cause mortality, compared to those who engage in at least 150 minutes of moderate‐intensity PA per week (Figure 3.3). A study by Lee et al. in 2012 revealed that physical inactivity can be deemed responsible for 6% of the burden of disease from coronary heart disease, 7% of T2DM, 10% of breast cancer, and 10% of colon cancer. Moreover, it was estimated that physical inactivity causes 9% of premature mortality, or more than 5.3 million of the 57 million deaths that occurred worldwide in 2008; if inactivity were decreased by 10% or 25%, more than 533,000 and 1.3 million deaths could be averted every year, respectively. Interestingly, using life‐table analysis, Lee et al. also showed that the elimination of physical inactivity would increase the life expectancy of the world's population by 0.68 years (Figure 3.4).

FIGURE 3.1 Trends in insufficient physical activity for three income groups from 2001 to 2016. The shaded areas show 95% uncertainty intervals.

Source: Reprinted with permission from Guthold et al. (2018).