24 October 2009

'Epidemic obesity' and the challenge for urban design

This follows on (belatedly) from a BLDGblog post looking at the potential for urban design to limit the transmission of epidemic disease. In essence, sit people greater-than-sneezing-distance apart and they're less likely to infect each other with flu. Reading this I started to think about what might be seen as the defining 'epidemic' of modern times: obesity. How do the spatial requirements for combating this epidemic differ from other diseases?

The obesity-as-epidemic theory refers in the broadest sense to the social character of being seriously overweight. It's rooted in analysis of the massive longitudinal Framlington Heart Study dataset (15,000 people since 1948), carried out by Nicholas Christakis and James Fowler. This dataset not only covers people's health outcomes but also their behaviours and friends & family networks, making it a powerful resource to understand the social transmission of ill health.

Christakis & Fowler's finding: people don't get fat in a vacuum; instead, obesity spreads from person to person. People have thought for a while that bodyfat has a substantial social life, rooted in the norms we learn about how to eat and what food means; cultural representations of ideal and non-ideal bodies; comfort eating, exercise and dieting as a means to virtue... But that was a sociological hunch, whereas now the Framlington data offers statistical evidence that this 'epidemic' metaphor might really be valid. Not only do children learn unhealthy eating habits off parents (and their peers) but, says the theory, an increased prevalence of overweight people around you makes it more likely you will be fat / gain weight / not be able to lose weight.

That's the theory. While the pattern it describes is pretty rigorous, it's not unproblematic to medicalise obesity as a disease in this way (something discussed more below). At this point in the discussion, though, public health policy operates upon the population rather than the individual, and under this lens obesity isn't bodily experience or personal narrative but yes, epidemiological. So, using this public health framework, how would we engineer the city to avoid the spread and transmission of obesity?

People tend to approach obesity as a problem of calories in versus calories out. Under this schema we would first need a city that increases exercise and activity levels. This means walking and cycling, and promoting this through such things as the Paris Velib scheme, tolls to discourage cars in the city centre, school 'walking buses', not selling school sports fields for housing development, and so on. Investment in suburban public transport could switch people's commutes from a car journey door to door to a bus or train ride - and walking to/from the station at each end. Buildings get designed with more stairs, fewer lifts, and showers for cyclists and runners. Council-owned gymnasiums get subsidised so they're free to use - and so on.

Calories in? Public health interventions here would act upon school dinners, and ensure poorer areas of housing were properly served with supermarkets and fresh-food grocers, not just fried chicken shops. You tax fatty food, sugar, processed stuff; subsidise British and/or organic farming better than current EU agricultural policy. The urban environment loses its billboards advertising junk food, and gains allotments and public farming co-ops with egg-laying hens clucking free. The public health case seems clear, and (alongside economic stimuli) urban design would seem to play as central a role in tackling this epidemic as it has historically in tackling more familiar infectious diseases such as typhoid or TB.

The problem is that 'calories in less than calories out' doesn't work as a strategy for diminishing obesity. It's counterintuitive and you won't believe me, so I'll direct you towards the fantastic discussions of peer-reviewed scientific research on this front on the NYTimes' science & health blog. It's not the place to go into it all here, but in short the factors driving obesity are A Lot More Complicated than food and exercise. Obesity still shows epidemiological patterns of transmission, but the vectors are much more complex.

So what does this mean for the 'urban hygiene' thesis sketched above that suggests 'epidemic' obesity can be tackled by urban design and spatial organisation in an analogous method to combating other infectious diseases? Basically that it's not going to work. Now, walkable cities and access to affordable fresh food are still social goods and by all means need promoting - but not necessarily because they're going to make fat people thinner. (They should make the population healthier, but that doesn't mean people will lose weight.) Instead the more rigorous solution might be to start thinking about obesity as the symptom rather than the illness.

The symptom of what? Poverty, and more than that, social inequality. At some point in the last century the West passed a tipping-point where food became sufficiently abundant that the poor could afford enough of it to get fat. Poverty being in these societies a largely relative state (even in governmental definitions such as income <60% of average), in more unequal societies the poor feel poorer - and are fatter. Why? Because, as humanity overlays biological nature with social meaning, food is about a hell of a lot more than calories or 'fuel'. It's about sociality, comfort and indulgence. Even those with very little can afford access to 'luxury'-marked foods that are rich with fat and sugar and highly pleasurable. The problem is not the food. It's the social structures that make people feel bored, and demoralised, and of little self-worth, and consequently likely to turn to over-consumption for some relief. Even rhesus monkeys do this: "Essentially, eating high-calorie foods becomes a coping strategy to deal with daily life events for an individual in a difficult social situation."

Under this improved understanding obesity is still 'epidemic' - because low social mobility reproduces the same conditions of inequality for the subsequent generation. And, as the famous Whitehall Studies of civil servants show, it is specifically inequality that is the problem, rather than simply low social status: the lower-ranking civil servants weren't poor, but they still had more heart disease, obesity and mortality than higher-ranking staff. Is urban design still able to act on this issue as it can upon epidemics? Yes... Maybe.

It's a lot harder to design out social inequality than it is to put some bike lanes in, that's for sure. For example, do you mix up housing sizes & tenures so rich live next door to poor - is that leveling and pro-equality? Or does it daily remind some people daily of much less they have, and would they be better off in areas of more homogenous income/class where similarity might facilitate greater community? How'd you spatially plan school catchment areas to enable equality of educational opportunity for all - and yet not bus kids halfway across the city, disrupting both social groupings and pupils' ability to walk/cycle/exercise their way to school?

Urban design is important for tackling social inequality, of that much I am sure. It produces the spaces in which different people interact and meet, it sets up the lived, experienced context for ideas of the public and the social commons and solidarity within the social collective. But the specifics of what you design and build and where, as means by which to tackle social inequality (and its symptom, 'epidemic obesity') - it seems a lot more difficult than the urban hygiene of sewers and clean water that beat epidemics of old.

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