Regular physical activity can provide a variety of health benefits – such as a decreased risk of depression and increased life expectancy. But what role does physical activity play when it comes to obesity? In this month’s newsletter, we examine the current body of literature on the connections between physical activity and obesity.
Extensive literature indicates that physical inactivity is associated with increased risks of coronary heart disease, type 2 diabetes, and breast and colon cancers. Inactivity also accounts for approximately 9% of premature mortality. In 2013, physical inactivity cost health-care systems approximately $53.8 billion worldwide, of which $31.2 billion was paid by the public sector, $12.9 billion by the private sector, and $9.7 billion by households. In addition, physical inactivity was responsible for 13.4 million disability -adjusted life years worldwide, and physical inactivity-related deaths contributed to $13.7 billion in productivity losses.
Children and adolescents are a group of concern when it comes to physical inactivity, due to high rates of sedentary behavior, including excessive screen time. Approximately 80% of adolescents worldwide are not sufficiently active (as shown in the figure below), and many adolescents engage in two or more hours of recreational screen time daily. Time spent in moderate-to-vigorous physical activity (MVPA) is inversely associated with changes in BMI from ages 9 to 15, and physical activity contributes to the attainment and maintenance of healthy weight among youth.
Source: van Sluijs
Physical activity plays a key role in weight loss, weight maintenance, and the prevention of weight gain and obesity; however, without changes in diet, very high levels of physical activity are necessary to achieve clinically significant weight loss as well as improved weight maintenance. While physical activity by itself does not appear to have a major impact on weight loss, it does have an effect on changes in body composition. A study of young adults found that while moderate-intensity and vigorous-intensity physical activity were not significantly associated with decreases in BMI over time, they were both significantly associated with decreased fat mass and decreased percentage of body fat in young adults with overweight or obesity. Physical activity also has an effect on health outcomes, independent of its effects on weight and body composition. Regular physical activity and exercise are associated with decreased risk of cardiovascular disease, type 2 diabetes, and cancer, all of which are common comorbidities of obesity. These benefits emphasize the importance of physical activity for people with obesity.
The built environment has a significant impact on weight outcomes, particularly among children. A study which evaluated favorable characteristics of neighborhoods for physical activity found that children living in neighborhoods with high physical activity environments, defined as having at least one high-quality park as well as built environments that were conducive to walking, with a high residential density, land-use mix, and street connectivity, had the lowest rates of overweight and obesity compared with children living in other neighborhood types. Another study that examined the same associations over time found that environments that were more walkable and recreation-supportive were associated with better child weight outcomes.
A variety of multi-disciplinary interventions can improve physical activity rates and subsequently reduce obesity among populations, especially for children who could benefit now, into adulthood, and for future generations. First, urban design strategies and city planning policies should focus on setting and achieving specific health and sustainability targets. The creation of walkable and cycling-friendly neighborhoods with accessible public open spaces can improve the health of populations and lower the risk of non-communicable disease. Schools also provide an important locus for physical activity. High quality sport and physical education programs can enable students to develop lifelong physical activity skills.
Finally, when it comes to implementing physical activity guidelines, it is critical that governments sustain their commitment and investments to physical activity and collaborate across sectors in their efforts to increase physical activity in their populations. The World Health Organization encourages governments to consider social and cultural contexts while communicating, disseminating, and implementing public health guidelines into national guidelines.