There are now far more obese people in the developing world than in richer countries. With the numbers of the obese and overweight nearly quadrupling in the past 30 years, developing countries need to understand the underlying structural factors driving this shift. While changing diets are identified as the immediate culprit, rapid urbanisation, auto-centric city planning, and shifting food supply chains are the little discussed and underlying drivers of this trend which must be considered.

According to a January 2014 report published by the Overseas Development Institute (ODI), 1.46 billion people, or one in three adults, are now overweight or obese. While this is a global problem, the increase has been more dramatic in the developing world (up nearly fourfold) than in the richer countries (up 1.7 times).

While some might argue that the developing world had some "catching up" to do on the obesity front, this pace of change is problematic for at least two reasons. First, many low and middle income countries continue to suffer from the burden of infectious diseases, and their health systems will now be further stretched by the increase in non-infectious diseases that normally accompany obesity. Second, several low-income countries continue to suffer from persistent food insecurity among their poorer members of society. As such, obesity represents a sort of misallocation of food resources that is bad for health on both sides of the equation.

While these twin double burdens (infectious and non-infectious diseases, as well as obesity and hunger) also exist in wealthy countries, their co-existence is now most pronounced in the developing world. As such, obesity in these countries is a public health concern that can no longer be seen as a minor nuisance. While the ODI identified changing diets as the immediate culprit, rapid urbanisation, auto-centric city planning, and shifting food supply chains are causal factors that must be better understood and addressed.

Structural Causes

Rapid urbanisation is one of the most significant trends impacting the planet today. While rural settlement patterns have dominated throughout human history, the world became majority urban for the first time in 2010. With the most rapid urbanisation rates occurring in the developing world, the planet is predicted to be 70 percent urban by 2050.

Urbanisation is known to drive a variety of dietary changes. People in urban areas typically eat more meat, sugar and fat than their rural counterparts. These shifts are made possible by higher average incomes as well as lower prices for such goods.

Urban folk also often face different work regimens and have less time for cooking. Such changes are even detected in the poorest of countries. My own research in Bamako, Mali revealed that women's reduced time for cooking was a major factor driving the shift to rice consumption. Even though rice is less nutritious than traditional staple grains, mainly sorghum and millet, its quick cooking time, and perception that it is a "modern" food, were highly desirable.

Also largely left out of ODI report on changing diets, is the role that urban environments play in shaping physical activity and the implications of this for obesity trends. Urban expansion, and associated urban planning, in middle income countries over the past 30 years, has been dominated by an auto centric vision.

For example, newer Middle Eastern cities are notoriously bad in terms of walkability. During recent trips to Riyadh and Kuwait City, I found it near impossible to walk from one destination to another. As such, only the wealthy with access to private gyms, or those engaged in physical labour on a regular basis, may lead everyday lifestyles that compensate for the effects of changing diets.

Finally, driven by globalisation, the supermarketisation trend has now hit much of the developing world. The research my students and I conducted in southern Africa, as well as that of others, explores the food security implications of the supermarket spread.

The Government of South Africa, for example, has embraced a neoliberal, supermarket proliferation approach as a means to improve food access. Unfortunately, the evidence in support of supermarkets is mixed as they often displace smaller shops and do not necessarily offer better prices. More problematic from a public health perspective are supermarkets' role in changing dietary patterns in the shift towards more processed foods.

Policy considerations

In terms of policy, public health professionals must collaborate with planners to address the structural factors driving changes in food consumption and urban physical activity levels. While urbanisation trends are unlikely to change, it is not too late to rethink city planning and food supply chains.

First, auto-oriented cities are a distinctly late 20th century phenomenon that have proliferated in the developing world. The obesity epidemic and climate change concerns suggest that urban planners ought to design for more walking and biking in the future. While bike lanes and sidewalks have often been considered a luxury only suitable for wealthy countries, using global climate change adaptation funds, as well as local monies, to support such infrastructure would be a win-win for public health and the environment.

Second, governments also ought to temper the neo-liberal approach to food insecurity which often encourages the proliferation of supermarkets in order to improve food access in poorer areas. Policies which encourage a mix of large and small food retail outlets may be better for consumers. Furthermore, encouraging the production of fresh fruits, vegetables and small stock in urban areas would also be better for local diets and the environment.

The quick rise of the obesity problem in the developing world is alarming and is, in some ways, a reflection of the rapid pace of development and globalisation. These phenomena have, ironically, introduced more circumscribed dietary regimes and urban living spaces, especially for poor and middle income households. The hope is that public health experts and planners may consciously work together to create more pedestrian friendly cities and diverse food systems.

William G Moseley is Professor and Chair of Geography at Macalester College in Saint Paul, Minnesota, USA. His latest book is An Introduction to Human-Environment Geography: Local Dynamics and Global Processes.

Follow him on Twitter: @WilliamGMoseley