A recently published study in The Lancet estimated that 40 percent of Americans will develop diabetes in their lifetime – a trend which is largely due to obesity and inactivity. Since the 1990s, some public health professionals have turned their attention to the potential offered by environmental modifications to fight obesity and improve population health. The same environmental modifications might positively impact another public health problem: depression.

“Obesity is a multicomponent disease arising from a complex interaction between genetic and environmental factors. However, the dramatic increase in obesity prevalence observed in the last decade seems attributable mainly to environmental changes promoting the intake of energy-dense foods, and/or reduced physical activity due to the high number of sedentary jobs, different transportation systems, and increasing urbanization,” observe Grave et al.

Mackenbach et al. echo this opinion, noting that “although genetic factors may underlie the propensity of individuals to become obese, the pace at which obesity prevalence has grown at the population level during recent decades points to social and environmental causes.”

Several studies have linked urban sprawl to obesity. Food advertising and rising stress levels have also been implicated. Other studies have shown that individuals eat 35 percent more when eating socially as opposed to eating alone, that fast paced music has the effect of encouraging people to eat more, and that lighting, hard surfaces, and colors are associated with greater food consumption. Environmental cues influence caloric consumption in addition to physical activity, which has led public health professions to consider the role of transportation infrastructure, sports facility placement, land use, green spaces, and other environmental factors in promoting population health.

Modifying individual behavior is often an uphill battle. Relapse can unravel previous efforts at any point in time. Grave et al. describe two factors required for behavior change: discrepancy and self efficacy.

The former refers to a perceived gap between current self image and an ideal or value-driven image. The latter, common to many models including the transtheoretical model, social cognitive theory, and protection motivation theory, refers to the “belief in one’s capacity to organize and execute the courses of action required to produce given attainments,” meaning individuals must feel adequately equipped to effect change. Self efficacy has been shown to predict the adoption and maintenance of healthy physical activity behaviors among adults. 

Promoting the adoption of new healthy behaviors often requires reinforcement. However, changes to infrastructure, such as increasing the price of parking and providing ample walking and biking paths can shape behaviors in ways that promote health.

The city of Montreal provides over 5,000 public use bicycles at 405 docking stations throughout the city, with clearly marked bicycle lanes and traffic signals for cyclists. Researchers conducted an impact evaluation based on the idea that “studies show associations between high levels of cycling for transportation or utilitarian cycling, and reduced traffic congestion, noise and air pollution, and obesity as well as an increase in physical activity,” and found that, once adjusted for rain and snow conditions, physical activity had increased as a result of the program. As many as 17.8 percent of survey respondents had used the bikes in the previous 7 days.

Another analysis based on a similar program in Barcelona estimated an impact of 0.03 incremental traffic deaths, 0.13 incremental deaths associated with air pollution, and 12.46 deaths avoided as a result of the increased physical activity.

Just as changing environment to counter the social isolation of cars and lack of physical activity can fight obesity, it also has the potential to address depression, which the WHO has indicated affects 350 million people. Globally, the prevalence of child and adolescent mental health disorders is an estimated 20 percent, led by depression. Brown et al. note that while pharmacological interventions and psychotherapy are common, they are often reported to be ineffective. Research has demonstrated that physical activity can have a protective effect against the onset of depressive symptoms as well as benefiting those with current symptoms.

Consequently, environments which promote good nutrition and encourage physical activity may fight depression in addition to diabetes, certain cancers, and cardiovascular disease. There is also a social dimension to walking, cycling, and other more physical forms of transportation, which has been shown to have a protective effect.

Diabetes and other obesity-related illness and depression are poised to consume a staggering amount of resources while resulting in significant loss of quality of life. Thoughtful urban planning with economic incentives offers the potential to modify behavior at the population level while offsetting some of the need for constant, ongoing intervention by providers at the individual level.

References

Brown, H., Pearson, N., Braithwaite, R., Brown, W., & Biddle, S. (2013). Physical Activity Interventions and Depression in Children and Adolescents Sports Medicine, 43 (3), 195-206 DOI: 10.1007/s40279-012-0015-8

Carlson, S. (2012). America’s Health Threat: Poor Urban Design. The Chronicle of Higher Education.

Freudenberg, N., Libman, K., & O’Keefe, E. (2010). A Tale of Two ObesCities: The Role of Municipal Governance in Reducing Childhood Obesity in New York City and London Journal of Urban Health, 87 (5), 755-770 DOI: 10.1007/s11524-010-9493-x

Fuller D, Gauvin L, Kestens Y, Daniel M, Fournier M, Morency P, & Drouin L (2013). Impact evaluation of a public bicycle share program on cycling: a case example of BIXI in Montreal, Quebec. American journal of public health, 103 (3) PMID: 23327280

Galea, S. (2005). Urban built environment and depression: a multilevel analysis Journal of Epidemiology & Community Health, 59 (10), 822-827 DOI: 10.1136/jech.2005.033084

Dalle Grave R, Centis E, Marzocchi R, El Ghoch M, & Marchesini G (2013). Major factors for facilitating change in behavioral strategies to reduce obesity. Psychology research and behavior management, 6, 101-10 PMID: 24124398

Gregg EW, Zhuo X, Cheng YJ, Albright AL, Narayan KM, & Thompson TJ (2014). Trends in lifetime risk and years of life lost due to diabetes in the USA, 1985-2011: a modelling study. The lancet. Diabetes & endocrinology PMID: 25128274

Mackenbach JD, Rutter H, Compernolle S, Glonti K, Oppert JM, Charreire H, De Bourdeaudhuij I, Brug J, Nijpels G, & Lakerveld J (2014). Obesogenic environments: a systematic review of the association between the physical environment and adult weight status, the SPOTLIGHT project. BMC public health, 14 PMID: 24602291

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