Does urban sprawl really make you fat?

If the link to this post from my earlier e-mail this morning didn’t work, this should (you might have to cut and paste the URL into your browser):


Does urban sprawl make us fat?

You can read the new post by The Melbourne Urbanist, Does urban sprawl really make us fat, at the new site at Crikey.

Should the war on obesity be a key objective of transport policy?

I know people who have the option of driving but instead take the train so they can improve their physical fitness. It takes longer than driving, but since they’re going to work anyway, walking to the station is an easy way to exercise. It makes good sense; I’ve walked or cycled to work at various times for the same reason.

However it’s one thing to make a private choice to use public transport in order to exercise – it’s another thing altogether to elevate the war on obesity and other health issues, as a matter of public policy, to the status of a key goal of the transport system. That’s what organisations like the Planning Institute and the National Transport Commission propose, but it’s not self-evident to me that it’s a good idea. It’s worth thinking about it further.

There’s a paradox here. The very point of public transport is to extend personal mobility. At the end of the nineteenth century when everyone other than the very wealthy walked, the arrival of trams and trains greatly enriched people’s lives by overcoming the limitations of walking. Now they could travel further to better jobs or better houses, take the family to the beach on Sunday, or visit friends and relatives in more distant suburbs. The whole point of public transport was to travel faster than walking so people could travel further in the same time.

The panoply of exercise-related issues like obesity are not a transport problem, they’re a social problem. They’re a result of eating more and of expending less effort in all aspects of life, not just in the way we travel. It’s true we are much more likely today to drive than walk, cycle or use public transport, but the avoidance of effort is true of almost everything we do.

Most of us work in jobs that don’t involve anything even remotely like the level of physical effort expended by the average worker of a few generations ago. If we did, Occ Health and Safety would have a fit. On the home front, we’ve had “labour saving” devices like refrigerators, stoves, washing machines and vacuum cleaners for generations. Television and home delivered newspapers mean we don’t even need to go out to get information and entertainment.

Consider the giant strides we’ve made in avoiding exertion over the last twenty years. Computers have eliminated the effort of going to the bank, the booking office, the travel agent or the bookshop. We blow leaves rather than rake them, we use power tools to drive nails and screws, we answer the phone without getting out of our seat, and we cook meals without having to prepare them. We control our air conditioners, central heating, TVs and sound systems with remotes. Climate control means our bodies don’t even consume much energy to keep warm – many children barely know what it means to shiver.

The decline of effort pervades all aspects of our lives, not just how we travel. For better or worse, it’s one of the ways we define progress. So transport – and that essentially means the car – is only one part of the health problem.

And in fact it’s a relatively small part, because the main cause of obesity is what we eat, not how little we exercise. It’s likely to be far more effective to target food than public transport.

Lennert Veerman, Senior Research Fellow at Queensland University’s School of Population Health, points to a recent study which argues the main force driving the obesity pandemic is an increase in consumption. He says the 1970s was:

When the food supply started to change radically. The supply of refined carbohydrates and fat increased and more food was mass prepared rather than cooked at home. The era of easily available, cheap, tasty, highly promoted, energy-dense foods had begun. This view of the causes of the rise in obesity prevalence suggests the likely solutions lie in the area of the supply and promotion of food. And research supports that notion.

He says if governments are serious about tackling obesity their priority should be food. They should tax unhealthy food, limit advertising and restrict availability in schools. He also says healthy food should be subsidised. Read the rest of this entry »

Has spare infrastructure capacity in the inner city disappeared?

Guess what this architectural gem in Stockholm is? Click to find out.

The received wisdom is it costs much less to provide infrastructure for an inner suburban dwelling than for one in the outer suburbs. However, as I noted last time, we don’t know how big the difference is or even, for that matter, if it’s positive or negative – we simply lack reliable evidence.

There are reasons, however, to suspect the savings in infrastructure outlays associated with urban consolidation might be much less than is widely thought. It’s plausible that the popular claim of an $85,000 per dwelling saving could be well off the mark (note I’m only talking in this post about the capital cost of infrastructure, not the economic costs and benefits of a fringe vs central location).

From the time urban consolidation was first seriously put on the table in Australia as a policy option, a key premise was the availability of ‘spare’ infrastructure capacity in the inner city. This part of the city had previously supported larger working class and migrant populations, so there was ‘free’ infrastructure to be had in support of a restoration of earlier population levels.

There’s not much sense in assuming any capacity is free (it all has to be paid for) but looking from the perspective of 2011, there are reasons to question if there actually is any spare physical capacity left, at least in relation to some types of infrastructure.

A key reason is a lot of whatever spare infrastructure capacity existed has already been used up by gentrification. At the 2006 Census, there were 36,488 more residents in the inner city of Melbourne than there were in 1976 (and 76,422 more than when the inner city was at its lowest ebb in 1991). In fact of the 31 municipalities in metropolitan Melbourne, only the City of Moreland and the adjacent City of Darebin had significantly fewer residents in 2006 than in 1976 – Moreland had 14,585 fewer and Darebin 17,137 fewer. That is not a lot in the context of projections Melbourne will grow from a current population of four million to seven million by circa 2049.

Even where there are fewer residents today than in the past, they might still have a much larger “infrastructure footprint” than their predecessors. Modern households have many more resource-intensive devices like flat panel TVs, air conditioners, heaters, computers, spas, and so on, than their predecessors. They have more cars than former residents, so there’s less room for parking. They also have higher standards – the primary school that used to accommodate 300 kids in six or seven classrooms now has to build twelve to handle the same enrolment.

Moreover, households today are smaller on average, so they have fewer ‘economies of scale’ in resource consumption than earlier generations. Two households of three persons each use more gas for heating than they would if the same six residents shared a single dwelling. Gentrifying households are also wealthier on average than the sorts of households who used to live in the inner city and inner suburbs 30 to 40 years ago. On a per capita basis, wealthier households consume more of just about everything worth having. Again, that will require more infrastructure capacity.

Thus it’s possible infrastructure in some locations could be at or above capacity even with a much lower population than those places housed in the 1970s. Read the rest of this entry »

Is inner city living the solution to obesity?

How much exercise is needed to burn off food?

It’s often pointed out that residents of the inner city, on average, are less obese than residents of the outer suburbs. Since the inner city is denser, more walkable and has much better public transport access than any other part of the metropolitan area, the conclusion seems obvious to many – a key strategy to address obesity should be to encourage higher dwelling densities and better public transport in the suburbs, especially the newer, fringe areas.

The flaw in this thinking is it fails to observe that the inner city – defined roughly as the area within 5 km of the CBD – is a different world. Relative to the suburbs, the inner city has an emphatic over-representation of younger, well educated and affluent residents with fewer dependents. The proportion of the population made up of young singles is three times that of the metropolitan area as a whole and there are twice as many young couples without children.

These are the sorts of people who on average are slimmer because they’re younger, who are of an age where appearance is enormously important, and who are well educated enough to know about nutrition and eschew fast food. They can afford to buy high quality fruit and vegetables and pay for gym memberships. Because they’re more affluent, they have fewer children on average and hence less need for a car.

They live in smaller dwellings so they can be near the CBD and take advantage of its enormous and unparalleled concentration of high-paying professional jobs, its matchless endowment of cultural attractions and its huge and diverse range of social and entertainment opportunities. There’s no other concentration of activity within the metropolitan area that comes even close to the richness of what the inner city offers.

Because they live at higher density, driving is too hard for many trips – roads are congested and parking costs range from expensive to impossible. So residents often walk or use public transport instead. That’s O.K., because they happen to live in that transit-rich, small and unique geographical area where every train line and tram line in the entire metropolitan area – the result of 130 years of construction and at least one spectacular land boom – converges.

So population density and access to public transport are not the underlying forces driving this group’s superior average BMI. Rather, it’s a combination of the small but highly specialised group who can afford to live there, on the one hand, and the special characteristics of the area, particularly the presence of the CBD, on the other.

It’s pie in the sky to imagine the sheer scale and complexity of the highly specialised attributes offered by the inner city could be replicated in the suburbs – much less the outer suburbs – within the foreseeable future. The inner city is focussed on the CBD and in almost every city in the world, the number of jobs in the city centre is an order of magnitude larger than any suburban centre (Atlanta is possibly the sole exception). In Australia, the centre offers the cream of corporate jobs.

The importance of proximity to the CBD in explaining the special character of the inner city is demonstrated by the fact walking’s share of work trips plummets from 13% in the inner city to just 2% immediately one locates in the adjacent inner suburbs. This share is only marginally better than the outer suburbs.

Will building at higher densities and providing better public transport in the outer suburbs significantly lower the incidence of obesity? Not likely. Even if all outer suburban dwellings were townhouses, the incentive to walk is much lower if there’s no CBD, cultural precinct, river, beach, historic buildings, hundreds of cafes, and hundreds of thousands of jobs to walk to. Perhaps most importantly, the outer suburbs don’t have the constraints on driving and parking that often make walking or public transport a superior alternative in the inner city. Read the rest of this entry »

Is it healthy to assume correlation means causation?

Association of obesity trend in the US with vehicles miles travelled (left) and with Justin Wolfer's age (right)

The link between the physical environment and health outcomes like obesity is fraught. The Victorian Legislative Council’s Environment and Planning References Committee should bear this in mind as it goes about its new inquiry into the contribution of environmental design to public health.

The Committee might want to start with the first chart in the accompanying exhibit, which comes from a recent issue of The Economist and purports to show that obesity has increased in the US in line with the increase in miles driven over the last 15 years. The chart is based on work done by researchers at the University of Illinois who found “a striking correlation between these two variables – but with a large time lag……This near-perfect correlation (99.6%) permits predictions about obesity rates”.

Expatriate Australian economist and Wharton business school Assoc Professor, Justin Wolfers, points out the folly of this claim. It is, in his words, a “nonsensical correlation”:

When you see a variable that follows a simple trend, almost any other trending variable will fit it: miles driven, my age, the Canadian population, total deaths, food prices, cumulative rainfall, whatever.

To demonstrate his point, Professor Wolfers prepared the second chart showing an even better correlation between changes in obesity over the period and changes in his age – he didn’t even need to resort to a time lag to get such a good fit! He acknowledges The Economist offered the customary caveat that correlation does not equal causation but this chart, he says, is so completely unconvincing as to warrant a different warning: “Not persuasive enough that you should bother reading this article” (in the interests of balance, here’s The Economist’s subsequent response to Professor Wolfer’s charge).

This exchange highlights a problem with much of the research that purports to show the physical environment — particularly density and/or public transport access —  has a strong effect on health-related variables like obesity. There’s plenty of evidence of correlation but not much evidence of causation. There’s no doubt obesity is inversely related to both density and access to public transport, but if it turns out these aren’t the underlying drivers of obesity then the economic cost of misdirected policies could potentially be significant.

There are special reasons why it’s hard to establish causation when dealing with real life infrastructure projects and transport/land use programs. These British epidemiologists reviewed 77 international studies examining the effectiveness of policy interventions to reduce car use. They concluded the evidence base is weak, finding only 12 were methodologically strong – and they mainly involved relatively small-scale initiatives like providing better information about travel options or direct financial incentives to reduce driving (incidentally, only half of those 12 actually worked i.e. reduced car use). Read the rest of this entry »

Must it be bright lights, big (dangerous) city?

Where Americans are moving - interactive map

This article in The Sunday Age reminds us that, for all its virtues, there’s a dark side to density. In Melbourne’s CBD, it include drunks urinating in doorways, assaults, noise and rubbish dropped heedlessly anywhere.

Physical proximity has driven human progress for millennia, driving trade and exchange. But it also brought severe problems, like the water-borne diseases that ravaged Victorian cities and the crime wave that plagued New York in the 70s and 80s. According to Professor Edward Glaeser, New York was so bad in those days that skilled workers required and got a premium – ‘combat pay’ – to work there.

Improvements in water supply and sewage disposal technology in the nineteenth century overcame cholera. Mayor Rudy Giuliano’s ‘zero tolerance’ policy, based on the ‘broken windows’ theory of George Kelling, is credited with turning New York into one of the safest cities in the world, at least partly because large numbers of young black men were incarcerated.

So you’d think Melbourne could solve its problems with marauding drunks. The Lord Mayor, Robert Doyle, says the long term answer is a change of attitude – we need to expect more of each other, he says. That’s actually not a practical answer because there’s not much agreement on what the underlying causes of anti-social behaviour are and what to do about them.

New York didn’t become much safer due to some change in the underlying causes of criminal behaviour. Partly it became too expensive to live in for practitioners of street crime. But a key factor appears to be ‘zero tolerance’ policing. That approach relied on the regularity that people who commit serious crimes are the kind who are also likely to flout minor laws. Those who committed minor offences like fare evasion were arrested rather than, as had been the case hitherto, ignored. Offenders were frequently found to have outstanding warrants for more serious crimes and accordingly ended up in gaol. I think it’s hard to avoid the suspicion that ‘zero tolerance’ is a bit like transportation to Botany Bay – a whole cohort of criminals was simply locked up.

However I don’t think the New York experience has a lot of relevance for Melbourne. We’re not dealing with serious crimes like stick-ups. The drunks who brawl and piss in King St at 2 am on a Sunday morning are more likely to be bank johnnies, tradies and public servants than career crims from ‘the projects’.  They’re more like ‘good ole boys’. Read the rest of this entry »