ABSTRACT
Behavior traits, such as physical activity, are generally accepted to be a result of environmental and genetic/biological factors. A large amount of literature (7, 18, 19, 38, 39, 43, 45, 47, 50, 52–56) has examined the environmental influence on physical activity. While the literature has focused on factors such as culture, peer influence, and the “built environment” (i.e., access to sidewalks) (5, 54, 56), it has been shown that the main factors contributing to the control of voluntary physical activity are genetic and biological influences (27). Voluntary physical activity is an important trait to study because it has been positively correlated with decreases in cardiovascular disease, obesity, type 2 diabetes, and some types of cancer (27). With only 3.5% of adults meeting the recommended physical activity guidelines (51), physical inactivity is the second actual leading cause of death (~250,000 cases/year) in the US with an estimated $507 billion a year in healthcare costs (34). Thus, the identification of biological mechanisms that regulate voluntary physical activity could improve the quality of life of individuals and potentially reduce healthcare costs.
