The Ecology of Overweight and Obesity
Obesity affects one in three Americans (Ogden et al, 2006) and has become a global epidemic in all industrialized societies (Low, Chew Chin, Deurenberg, 2009). In the United States alone, 64% of non-Hispanic whites, 76% of non-Hispanic blacks, and 76% of Mexican Americans are overweight or obese, with higher rates of overweight among men, and higher rates of obesity among women (Ogden et al, 2006). The overweight and obesity epidemic is primarily attributed to lifestyle and environmental changes that have occurred in the industrialized world in the last three decades, and is largely preventable with early and broad based intervention efforts. Overweight and obesity are associated with numerous chronic health illnesses, including coronary heart disease, cancer, stroke, and diabetes, four out of the ten leading causes of death identified by U.S. sources (Department of Health and Human Services [DHHS] 2008), and echoed by international bodies (World Health Organization [WHO], 2008). In the USA, roughly 300,000 deaths and $120 billion in medical expenses are attributed to obesity and obesity-related conditions annually. Over half of these expenses are paid for by Medicare and Medicaid, with each U.S. taxpayer responsible for about $200 per year for obesity-related medical costs. From an employer’s perspective, medical costs are 77% higher for obese employees than healthy employees, costing employers over $8,000 per person per year (Centers for Disease Control and Prevention [CDC], 2008).
Numerous individual approaches to weight control have been tried, and found effective, but typically only for a very short period of time. People find it hard to stick to restrictive diets and rigorous exercise programs, suggesting that lifestyle approaches that emphasize moderation may be a more realistic way to live a healthful life. However, even moderate approaches may be ineffective when there is little support for healthful living and are few opportunities to eat healthfully and be physically active. Ecologic models provide a structure to account for multiple levels of influences and the linkages and processes among them. Ecologic models encompass everything both internal and external to the individual and have recently begun to show promise for guiding research and practice across a variety of health domains. Spence and Lee (2003) have described the Ecological Model of Physical Activity that conceptualizes influences on physical activity as micro-, meso-, exo- and macro-environmental and suggests individual level health behavior and disease states as outcomes. Lee and Cubbin have provided an updated, visual model in their recent work (2009) to help consider how ecologic models can be broadened in scope to consider not only physical activity but also dietary habits and obesity as outcomes.
Micro-environments are the immediate environments in which humans live, work and play and may include the home, work, school, cafe, store, restaurant, park and many more. The micro-environments may be thought of as relatively static, but these are linked by dynamic meso- and exo- environmental linkages and processes. The linkages and processes may be social interactions, such as a conversation, or actual physical linkages. Meso-environmental elements directly connect two or more micro-environments together, such as the physical roadway between the home and the park. Exo-environmental factors indirectly link micro-environments. For example, dietary habits that occur in the cafeteria at a child's school (micro-environment of the child, but not the parent) may impact the dietary habits of parents and friends of parents in the workplace (micro-environment of the parent but not the child), by way of a shared conversation between the child and parent. The macro-environmental factors are broad overarching factors such as municipal designs, policies, transportation systems, social and cultural norms and many other factors. All of these environments lie within the ecologic milieu and are influenced by extra-individual forces of change (e.g., technological innovation), and intra-individual factors that are biological and psychological in nature. Ecologic models provide a useful heuristic to conceptualize and investigate the multiple physical, social and virtual environmental factors that influence health behaviors.