From the Director

Understanding the Puzzle Pieces of the Obesity Epidemic

Much has been written about the obesity epidemic in the United States and its rapid march into other industrialized societies. Obesity is one of the most pressing public health threats facing us today. One-third of children and two-thirds of adults in the United States are overweight or obese. ⁽¹⁾

Obese adults are at increased risk for a number of chronic conditions, including type 2 diabetes, hypertension, heart disease, stroke, arthritis, liver and gallbladder disease, sleep apnea, and some types of cancer. Stigmatization of overweight individuals has been documented and includes discrimination in hiring. ⁽²⁾ Childhood obesity can lead to many of the same chronic conditions found in obese adults, as well as orthopedic problems and asthma. Obese children also are more likely to be teased and to suffer from low self-esteem and depression. These children also have a greater risk of becoming obese adults.

This epidemic also creates economic burdens. According to some estimates, rising obesity rates and the medical consequences account for as much as one-quarter of the increase in health care spending in the United States between 1987 and 2001. ⁽³⁾ One estimate projects that obesity will account for 16 percent of health care expenditures by 2030. ⁽⁴⁾ Lost productivity costs are even greater. ⁽⁵⁾

Nobody chooses to be obese, so why is it so hard to prevent, and once it has occurred, why is it so hard to reverse? If only the answer were as simple as telling people to balance their energy intake and energy expenditure. Unfortunately, the complexities of human biology and behavior—and their interface with the environment—limit the efficacy of linear or single-solution interventions.

Obesity is the product of multiple interacting factors, ranging from genes to behaviors to the physical and social environments. Although individual behaviors – specifically food intake and physical activity – play a central role in the obesity epidemic, the epidemic cannot be fought through targeting individuals alone. Because individuals vary in their genetic predispositions and learned habits, behavioral interventions may not work equally well for all. And the very best behavioral interventions may not work for long in the context of our obesogenic environment, with its abundance of low cost, energy-dense food and sedentary lifestyles. As our experience with combating tobacco use has shown, policies or interventions aimed solely at individuals and at increasing the number or type of small-scale interventions will not be sufficient. “If humans have built-in biological propensities at odds with their environment, top-down approaches may be needed to achieve population obesity prevention goals”. ⁽⁶⁾

The reality is that obesity is not just a personal health problem; it is also a systems problem. This means that researchers must seek ways of altering behaviors that are intertwined with broader social, cultural, physical, economic, and political environments. Behavioral and social scientists have a long history of studying how these environments are shaped by individual and social action, and how individual behavior is influenced by features of the environment such as cultural norms, economic incentives, and the physical layout of communities. In recent years, researchers have studied the effects of fast food outlets ⁽⁷⁾, access to recreation facilities ⁽⁸⁾, school policies ⁽⁹⁾, family feeding practices ⁽¹⁰⁾, and social networks on behaviors related to obesity. ⁽¹¹⁾ Behavioral scientists have also studied how genetics, the brain, and environments interact to shape individuals’ eating and physical activity preferences and habits. ⁽⁶⁾

One of the biggest public health challenges is how to get a sense of the “big picture” of all the factors that influence obesity rates. Although we are developing a piecemeal understanding of the various contextual factors involved in obesity, we do not yet understand how these multiple levels of risk interact with one another and with biology. One approach is the use of systems science methodologies or principles, which provide a way to address complex problems, while taking into account the “big picture” and context of such problems. These methods enable investigators to examine the dynamic interrelationships of variables at multiple levels of analysis (e.g., from cells to society) simultaneously, while also studying the impact on the behavior of the system as a whole over time. Systems science methodologies can help us understand why programs and interventions fail to have their intended effects, and why, in some cases, they can even make the problem worse.

Where should we focus our research, so that we can better invest our public health dollars?

We need to continue to build the knowledge base needed to inform the development of systems science research on obesity. This includes more basic research on how families and communities influence diet and physical activity, particularly in children; understanding how cultural norms relevant to these behaviors are acquired and changed; and better identifying the causal paths linking built environments to individual behaviors. We need to integrate our expanding knowledge through the development of systems science models and evaluate and refine these models in the light of new data and insights.

We need to translate these research-informed models into practice by using them to guide multi-level prevention approaches that reach into health care, school, workplace, and community settings. We must invest in research on upstream policy interventions and their downstream effects. For example, can nutrition assistance programs, nutrition and menu labeling, altered advertising, taxes on junk food, increased physical activity in the workplace and schools, and reformed transportation policies start to turn the tide? What is the potential for other broad-scale approaches, such as social and commercial marketing, for changing our cultural views of obesity and obesity-related behaviors? We must also evaluate the potential for innovative individual behavioral approaches for weight control or maintenance in the context of diverse environments.

Finally, we need to recognize that the initiation and maintenance of behavior change can be extremely difficult, and even those interventions that succeed in controlled clinical trials do not always transfer well into the uncontrolled environment in which we live. Not only do we need to build supportive environments, we also need to develop better delivery channels and systems in place to disseminate effective interventions to the public, policymakers, and other decision makers to ensure that they are implemented, adopted, and maintained.

The National Institutes of Health’s Office of Behavioral and Social Sciences Research is working to make this research agenda a reality. We have co-funded conferences exploring psychological, neurological, and social factors affecting eating behaviors; social science contributions to understanding family dietary practices, and multi-level approaches to combating childhood obesity. We have partnered with several NIH institutes on funding opportunity announcements for methodological, basic, and translational research on obesity. We have established a partnership with the Centers for Disease Control and Prevention, the Robert Wood Johnson Foundation, and other NIH partners to facilitate the translation of obesity science into effective prevention strategies.

OBSSR promotes an interdisciplinary perspective to improve our understanding of the forces that determine optimal health promotion and prevention, reduce disease burden, and improve chronic disease management. Tackling the obesity epidemic requires that we use scientific evidence from a wide range of disciplines in order to identify the broad range of factors that influence obesity. Building a shared understanding of the various pieces that make up the obesity puzzle is a critical step towards developing effective solutions.

1. Ogden CL, Carroll MD, Curtin LR, McDowell MA, Tabak CJ, Flegal KM. Prevalence of overweight and obesity in the United States, 1999-2004. Journal of the American Medical Association 2006; 295(13):1549-1555.
2. Myers A, JC Rosen. Obesity Stigmatization and Coping: Relation to Mental Health Symptoms, Body Image, and Self-Esteem. International Journal of Obesity and Related Metabolic Disorders 1999; 23:221–230
3. Thorpe KE, Florence CS, Howard DH, Joski P. The impact of obesity on rising medical spending. Health Affairs 2004: W480-W486.
4. Wang Y, Beydoun MA, Liang L, Caballero B, Kumanyika SK. Will all Americans become overweight or obese? Estimating the progression and cost of the US obesity epidemic. Obesity. doi:10.1038/oby.2008.351.
5. Sugarman SB, et al. The Economic Costs of Physical Inactivity, Obesity, and Overweight in California Adults: Health Care, Workers’ Compensation, and Lost Productivity. California Department of Health Services. April 2005.
6. TT-K Huang, TA Glass. Transforming research strategies for understanding and preventing obesity. Journal of the American Medical Association 2008; 300(15):1811-1813.
7. Davis B, and C Carpenter. Proximity of Fast-Food Restaurants to Schools and Adolescent Obesity. Am J Public Health. 2008 Dec 23. [Epub ahead of print]
8. Kligerman M, Sallis JF, Ryan S, Frank LD, Nader PR. Association of neighborhood design and recreation environment variables with physical activity and body mass index in adolescents. Am J Health Promotion, 2007; 21(4):274-7.
9. Gortmaker SL, Peterson K, Wiecha J, Soal Am, Dixit S, Fox MK, et al. Reducing obesity via a school-based interdisciplinary intervention among youth. Archives of Pediatrics and Adolescent Medicine, 1999; 153(4):409-418.
10. Kitzmann KM, Beech BM. Family-based interventions for pediatric obesity: methodological and conceptual challenges from family psychology. J Fam Psychol. 2006; 20(2):175-89
11. Christakis NA, and JH Fowler. The spread of obesity in a large social network over 32 years. NEJM, 2007; 357(4):370-379.