Transportation, urban design, and land use as syndemic drivers
Transportation systems, urban design, and land use are interconnected systems that have an enormous effect on climate change and obesity through their effects on greenhouse-gas emissions, physical activity, and diet.
Transportation accounts for approximately 14% of greenhouse-gas emissions.124 Car use has been associated with an increased risk of obesity,125 and changes in commuting from cars to active or public transportation have been associated with reductions in BMI.126 Furthermore, reduction in carbon dioxide emissions through reduced motor vehicle use and increased active travel (eg, bicycling or walking) exceeds the reduction in greenhouse-gas emissions that could be expected from increased use of lower emission motor vehicles.127 Transportation systems and community designs that support active transportation, reduced car use, and access to healthful foods are triple-duty actions for The Global Syndemic.
Urban design and land-use planning involves shaping, building, or retrofitting the built environment, open spaces, residential and commercial buildings, and transportation systems at city and neighbourhood scales. Urban design relies on the use of tools, such as land-use zoning and planning layouts of streets, roads, transportation, public spaces, and residential and commercial areas. In recent decades there has been increasing recognition of the many ways in which urban planning and design can affect human health.128 Additionally, the challenges of global environmental change make it essential that cities become more sustainable, and many overlaps exist between health and sustainability at the urban level.129 Re-establishing the link between urban planning and public health is a high priority, although the evidence base for this association is overwhelmingly from high-income countries and it receives surprisingly little attention in LMICs.130
Urban and rural environments are changing rapidly. In 1990, an estimated 43% (2·3 billion) of the world’s population lived in urban areas. By 2015, urban populations had grown to an estimated 54% (4 billion).131 The changing economic and governance conditions in the past few decades have tended to increase segregation and inequities in cities and towns and made them increasingly dysfunctional living environments for many residents.132 Although affecting all regions of the world to some degree, these processes have been most tangible in megacities in LMICs, where “huge office complexes linked to world financial markets, gated residential estates for the wealthy, and luxurious leisure playgrounds for the rich and famous have taken centre stage in city building, under circumstances where the poor and marginalised are pushed aside, allowed to languish in poverty and destitution in impoverished ghettoes in the ‘in-between’ places of the city”.133
The appropriate planning, design, or retrofitting of built environments and transportation systems can facilitate and promote safe outdoor physical activity and active transportation. In addition to growing mass transit and safe commuter cycling, neighbourhood-scale interventions can promote physical activity. These interventions include designing new neighbourhoods with a fine-grained street network, a mix of land uses and destinations, a range of appropriate public spaces for recreation, upgrading pavements and public spaces (eg, better paving and the planting of trees), building bicycle lanes, and improving street lighting.134, 135, 136 Neighbourhoods also need to be designed to be safe, through having eyes on the street for example, to ensure that outdoor spaces can be used without fear of crime and violence. In cities that have low densities, densification and compaction of buildings can create mixed-used environments with a range of destinations to which people can easily walk and cycle. Cities such as Bogota, Colombia, and Curitiba, Brazil, are notable examples that have focused investment on public transportation, and have improved the living environment of low-income residential areas through participatory planning and budgeting processes, investment in neighbourhood parks, and the promotion of non-motorised transportation.137, 138
A recent Lancet Series formalised these observations by concluding that eight regional and local interventions would promote walking, cycling, and public transportation and reduce car use.139 These interventions included access to desirable destinations, decreasing demand for car use by reducing the availability and increasing the cost of parking, designing networks that encouraged walking and cycling, increasing residential density, increasing access to public transportation, increasing the attractiveness of active travel through the creation of safe neighbourhoods and safe affordable and convenient public transportation, and providing equitable distribution of employment across cities. Pavements, bike lanes, and streetscapes that include green canopy cover have a double benefit of making opportunities for physical activity more attractive and increasing uptake of carbon dioxide by plants and trees.
Urban and rural areas are closely interlinked in many ways and have several effects on one another, so interventions in urban areas need to be accompanied by interventions in rural areas. A high priority is the reduction of periurban sprawl, which can have negative effects on ecosystem services and the land available for agriculture.
Urban design and food systems
In some cities in high-income countries, land-use zoning can create urban environments that promote food systems for healthy and sustainable diets. Strategies include the promotion of urban agriculture, government regulation of the location, nature, and size of food and restaurant outlets (although the evidence for the effectiveness of this intervention is mixed), and incentivising food retailers and restaurant outlets that sell healthy products to relocate to low-access areas.140
In LMIC cities, the high degree of informality leads to weak government regulatory approaches, such as land-use zoning, and therefore less direct infrastructure provision and implementation of projects that shape urban environments. Upgrading market places, designing suitable spaces and providing appropriate infrastructure (eg, water supply and protection from the sun) for preparation and sale of street food, creating suitable spaces for urban agriculture, and providing access to resources for low-income households to become involved in urban agriculture are all ways to increase food security and promote healthier diets in cities in LMICs (appendix p 23).141 The urban design contexts in high-income countries and LMICs develop differently in the creation of food deserts and food swamps (panel 9).
In some cities in high-income countries, residential segregation and land-use zoning can result in low-income people living in food deserts characterised by a relative lack of healthy and nutritious food options or food swamps characterised by an excess of fast food chains and food outlets selling processed foods.142, 143 For example, a study of two US localities found that obesity was more prevalent in areas with more fast food outlets and small grocery stores and less prevalent in areas with more supermarkets.144
Food deserts are rarer in cities in low-income countries, where traditional marketplaces and informal vendors have an important role in food systems, and land-use zoning has less influence on actual land use because a substantial proportion of land use is informal, resulting in slums and other informal settlements. Generally large numbers of informal food retailers exist in low-income areas, but they are still “poor, often informal, urban neighbourhoods characterised by high food insecurity and low dietary diversity, with multiple market and non-market food sources and variable household access to food.”145 The net result is that, for most residents of low-income areas, getting sufficient and healthy food to eat is a constant struggle.146
The rapid growth of supermarkets in low-income countries might exacerbate this problem by competing with the small retailers and encouraging consumption of inexpensive processed foods.147, 148, 149 Food system power asymmetries need to be addressed through policies and subsidies to empower small and medium farmers, local and regional markets, and short food chains. These producers and the diversity of their products are excluded from big food chains dominated by big food and supermarket corporations. Small and medium farmers and local and regional markets maintain food diversity (eg, vegetables, fruits, and grains) that are the base of traditional cuisines and diets. These forms of agriculture reduce the greenhouse-gas emissions and can reduce agrochemical use. The scarcity of infrastructure and oversight for markets and food vendors in low-income countries can also result in food contamination, with its associated health risks.150 Finally, in both high-income countries and LMICs, urban sprawl in periurban areas can have a negative effect on food production, resulting in the loss of agricultural land and ground and water pollution.151
Planning, development, and retrofitting
Ultimately, governance systems and processes need to become more collaborative to ensure that the views and interests of all key stakeholders are adequately included (discussed in the governance challenges section). Within governance processes, however, particular urban planning decisions contribute to reducing obesity and undernutrition while simultaneously strengthening climate change mitigation and adaptation. The Lancet Series on Physical Activity identified a critical need to improve decision making by policy makers, and made a number of recommendations for improving the translation of research into practice that could inform the decision-making process.152 These recommendations included identification of policy-relevant research questions, development and implementation of policy-relevant research methods, dissemination of strategies to decision makers, and engagement in advocacy. Each recommendation included strategies and steps for implementation. In addition to these recommendations, several other crucial areas deserve attention. At the national level, in countries such as the USA, subsidies for fossil fuels keep petrol prices artificially low, thereby encouraging car use and providing no incentive to invest in active and public transportation. A second important challenge is how to incentivise developers to incorporate healthier and more environmentally-friendly designs in new developments. The third challenge is that the design of new communities and neighbourhoods rarely take into account the needs of marginalised populations. The absence of public transportation and the distance between where workers live and where their jobs are located leads to lengthy commutes and potentially underemployment. Holding governments accountable for decisions related to transportation, urban design, and land use will require greater awareness of the adverse health effects and environmental effects and the true costs of current practices.
Urban design and land use reflects the various underlying social and economic conditions and governance systems under which they have developed, resulting in very different types of urban and rural environments in different parts of the world. For example, there are some compact and dense cities that are suitable for walking and cycling, sprawling cities dominated by freeways for cars, formal housing areas with good quality housing and services, overcrowded slums with a lack of basic services, high-density subsistence farming areas and low-density commercial farmland.
Most large cities are forced to address the pressing twin challenges of traffic congestion and air pollution and many are showing progressive leadership in these areas. Switching reliance on cars and trucks to more public transportation, active transportation, and rail freight will address the targeted issues of congestion and air quality as well as reduce greenhouse-gas emissions and increase physical activity. The next logical step is leadership on climate change itself, which many cities have done through the C40 initiative that now has 96 affiliated cities covering 25% of the world’s GDP,153 and other platforms, such as WHO’s Healthy Cities154 that has more than 1000 affiliated cities. This collective leadership across cities will serve to activate national actions on climate change as well as fill the gaps in areas in which national actions are weak. Although evaluation of the attributable impacts of healthy city approaches is challenging,155 such initiatives can create the collective momentum among leaders, translating, in theory, into societal and infrastructure change.
Effects of physical activity recommendations on climate change
WHO recently published a set of recommendations for increasing physical activity, many of which aimed to improve built environments, access to recreation, and other infrastructure to support active recreation and commuting for health (table 2; appendix p 24).156 Most of the existing recommendations to increase physical activity for health might also have some benefits for climate change mitigation and adaptation. Apart from specific transportation infrastructure strategies, the estimated potential effect of each strategy is likely to be small. However, the collective effects could be substantial. If these strategies were consciously revised as double-duty actions, they could produce more substantial effects.
Country contexts for action
Countries and regions operate under very different contexts in relation to their progress on achieving the global outcomes of economic prosperity, human health, social equity, and environmental sustainability (figure 2A; figure 3; appendix p 4), affecting their priorities in addressing The Global Syndemic.
The focus of many countries is economic growth, and the top priority for low-income countries is reducing poverty. Many internal systems and development aid are focused on supporting businesses to create individual, community, and national prosperity. Although global indicators clearly show a rise in income, wealth, and living standards over time,161 the major caveat is that increasing prosperity has been shared very unevenly, and in some areas, wealth creation has occurred at the expense of health loss (eg, economic activity from the tobacco, alcohol, and unhealthy food industries). Central to continuing improvements in prosperity is the creation of business models that incentivise restoration and sustainment of human and ecological health and wellbeing, because the dominant business models of the 20th century have been too destructive, especially in over-extracting the planet’s resources and overwhelming its carrying capacity in many areas, including greenhouse-gas emissions. One of the future effects of climate change is the severe threat it poses to economic prosperity.
Natural ecosystem health and wellbeing
In recent geological timespans, the global ecosystem has remained relatively stable, notwithstanding the semi-regular cycles of the ice age. However, when explorers inhabited virgin territories that had no previous experience of humans, such as the Americas, Australia, and New Zealand, pockets of population explosion, loss of habitat, and species extinctions rapidly followed.162
This disruption and overburdening of ecosystems is now occurring at a global scale, and human-induced climate change is accelerating at a rapid rate driven by increases in population numbers and consumption.163 In general, the carbon footprint and GDP are inversely related to each other, and no country or region is in the best tertile for both indices (table 3; appendix p 4).
Table 3 Descriptions of complementary factors of current or past public health actions related to tobacco, alcohol, gun control, traffic safety, and infant nutrition and implications for making progress on obesity
|Relevance to The Global Syndemic||Issues|
|Leaders of major movements or campaigns are typically highly committed and politically savvy individuals who galvanise community support, motivate and organize collective efforts, and counteract powerful opponents||Strong leadership from academia, civil society, and government has already had important roles in generating support for government action on obesity prevention, community design, and climate change, and will continue to be needed even after initial successes become evident||Tobacco, gun control, infant nutrition164, 165|
|Trend data and modeling can demonstrate the effects of a problem, generating attention and support for action. Research can demonstrate causes, point to potential actions, and reduce uncertainties that opponents might use to delay change. Legal research helps to avoid and overcome court challenges by opponents||Data and models demonstrating the harms associated with The Global Syndemic can be used in media and other advocacy communications to support demands for action. Evidence is needed to document outcomes from double-duty or triple-duty actions. Evidence opposing policy change generated by vested interests can intentionally confuse the picture||Tobacco, alcohol164, 165|
|Transition from a focus on individual behaviour to the environments in which the behaviour takes place. Individual responsibility remains in frame but becomes secondary to collective and environmental action||The use of an obesogenic frame emphasises the role of the broader environmental determinants of obesity rather than blaming individuals with obesity. Broadening the frame of obesity to include transport, urban design, and climate change can create a broader base of support for policy change||Tobacco, alcohol, gun control, traffic safety164-166|
|Focus on industry|
|Emphasis on the role of industry can encourage mobilisation and collective action. Industry often counteracts this process by giving a misleading impression that they are acting in the interests of public health||Activism that takes a hard line against business models that market high-calorie, nutrient-poor foods and beverages is a necessary component of effective efforts to curb the obesity epidemic. The primacy of profits over health and a focus on costs that account for environmental impact of transport, land use, and food production could shift the focus from individual responsibility to corporate and government negligence||Tobacco, gun control, traffic safety, infant nutrition164,166–168|
|Protection of vulnerable populations, particularly infants and children, resonates strongly with the public and with policy makers||A focus on the effects of aggressive marketing of high-calorie, nutrient-poor foods and their contribution to childhood obesity can mobilise parents, civil society groups and legislators in support of policy change. Educating children about the effects of climate change on their current and future environment might influence adult behaviour, as has been the case with tobacco||Tobacco, gun control, traffic safety, infant nutrition164,168,169|
|Among adults, an emphasis on special efforts to effect actions for populations living in poverty or with other social disadvantages, in addition to whole-of-population strategies, can allow for fairness arguments and moral power. This approach might mobilise certain special interest groups as well as the broader population||Socially disadvantaged communities are disproportionally affected by undernutrition, climate change, and increasingly by obesity. Fair and just opportunities for access to healthy food, options for physical activity, and a healthy environment are often less favourable in the physical and economic environments of these communities||Tobacco, alcohol164|
|Taxation of sugary drinks, elimination of subsidies for fossil fuels, and paying the true costs of petrol and meat might be perceived as regressive. The regressive nature of taxes can be countered by earmarking taxes to provide related services to low-income communities (eg, using tobacco tax revenues to pay for smoking cessation programmes)||Arguments that taxes on sugar drinks or high-calorie, nutrient poor foods are regressive are countered by their progressive effect on health, creating greater health gains for those with less income through larger gains in health-related behaviours, and by strategies that direct tax revenues to community benefits, such as providing potable water in schools, subsidising the purchase of healthy foods, increasing access to parks and recreational facilities, or increasing access to early childhood education. Paying the true costs of petrol and meat will increase their costs and reduce consumption||Tobacco, alcohol164|
|Interest groups and coalitions|
|Broad based coalition-building can happen at all levels to galvanise a community, overcoming competition between risk-factor or disease communities and combining forces to address issues of mutual interest||Initiatives led by interest groups acting in coalitions have effectively succeeded in taxing sugary drinks and supporting controls on food marketing to children. Increasingly, groups are forming in which patient advocates work with health and research professionals around public education, protection from discriminatory policies, and advocacy for changes in health-care delivery systems||Tobacco, alcohol, infant nutrition164–166, 168–170|
|Activists grouped en masse can cut through barriers to political action by seizing the attention of policymakers. Self-help groups of people directly affected by the issue are especially effective||Focusing on obesogenic environments counters arguments about personal responsibility for obesity. Movements around community livability can include walking or cycling, which are double-duty actions for The Global Syndemic||Alcohol166|
|Leveraging local control|
|National movements have usually begun at the local level. Government ordinances at the state or local level confer benefits on small communities along the way to broader social change||In many cases local governments are adopting obesity prevention policies and taking regulatory actions to address obesogenic food environments. For example, California, USA, is maintaining fuel efficiency strategies that reduce greenhouse-gas emissions despite efforts of the federal government to loosen those standards. These strategies provide precedents for action that can be used by other localities||Tobacco, alcohol, gun control164,169|
Human health and wellbeing
In the past century, almost all global indicators of human health, such as life expectancy, maternal and infant mortality, and deaths from infectious diseases, have been heading in the right directions, albeit with a number of caveats. The first caveat is that improvements have been much more substantial for wealthy populations than poor populations. The second is that obesity and diabetes are major diseases that are still increasing in all countries. Finally, climate change and the loss of the ecosystems on which we depend are the largest health risk in the future.39 South Korea and Switzerland are the only countries in the best tertile for both low prevalence of obesity and underweight (appendix p 4).
In the absence of robust democratising institutions, human societies tend towards inequalities of wealth and power, because the powerful tend to create and maintain societal conditions to support their power. The two World Wars and intervening Great Depression reduced the wealth inequalities somewhat.171 But in the past 50 years of rapid globalisation, an increasing concentration of power and wealth in the hands of a small number of individuals and corporations has occurred. Since the 1980s, the rise of neoliberal governance approaches has been the dominant political and economic paradigm of democracies. Neoliberalism involves the government deregulation of markets, small government, and reduced social protections, and has resulted in a growth in asset wealth far exceeding rises in salaries and wages, causing a resurgence of increasing inequalities within and across countries.161, 171, 172 Climate change has led to major weather events, crop failures, food insecurity, and other adverse health consequences. The effects of climate change will be more pronounced for poorer people living in LMICs, and will further escalate existing social inequities.