The prevalence of obesity has become a major public health concern in the U.S. The growing numbers of obese children and adults, along with obesity-related diseases and health problems have contributed to a tremendous increase in U.S. healthcare costs. Hence, combating rising obesity levels is a critical undertaking for the nation. There is sufficient evidence to support the claim that the decline in physical activity is a key contributor to the obesity epidemic. Commuting to work is an important means for regular physical activity. Walking and bicycling for daily transportation are important sources of physical activity. Commuting to work by public transportation may also lead to a substantial level of physical activity through walking or riding to a transit station or transit stop. Despite the significant health benefit of commuting to work by walking, bicycling and public transportation, driving by private car to work has been the dominant mode of commuting to work in the U.S. since the 1960s.

A few studies have found that automobile dependence and the dramatic decline in active transportation (walking, bicycling and public transportation) contribute to the rise of obesity. However, these studies are based on either local survey evidences or national aggregate census data. Research on examining the relationship between modes of transportation to work and obesity rates at the U.S. state level is scarce. This void in the research is important because obesity rates vary widely across the American states. Anecdotally, states with the highest levels of obesity generally have the lowest shares of active transportation and highest reliance on automobile travel. Therefore, it is important to empirically examine this variation in obesity rates among states with a focus on transportation factors. To fill the gap in the literature, the main objective of this research is to explore the relationship between transportation mode choices and obesity rates at the American state level. This study will use a panel data set consisting of 50 U.S. states from 2000 to 2010. Data for the variables of means of transportation to work will be collected from the American Community Survey and U.S. Bureau of Transportation Statistics. Data for the variables of state obesity rates will be collected from the U.S. Centers for Disease Control and Prevention. The socio-demographic data will be collected from the U.S. Census Bureau.

Given the widely expressed concern about the epidemic of obesity, research about the effects of transportation mode choices on obesity rates is especially timely and important. The research will make significant contributions to the fields of public health and transportation policies in several key ways: to expand theoretical understanding of the determinants of obesity rates, to explore how transportation mode choices matter for obesity rates, and to offer practical policy suggestions for combating obesity by integrating public health objectives into the transportation planning and investment process.