Is obesity really caused by suburban sprawl?

Why would households burdened by mortgage payments and childcare costs forgo the cheaper prices available by driving to bigger centres, in favour of the higher cost at a local convenience store? And what does “convenience” really mean anymore? The use-by date on fresh milk at my Safeway is around 10 days and UHT milk is ubiquitous. There’s obviously a market for stores like 7-11, but last time I looked mine didn’t sell fresh vegetables or fruit, the very things that do go off quickly. Now that smoking is out of favour, I don’t see much hope for small walking-based convenience stores in new estates.

I think many more kids could walk or cycle to school both in the outer suburbs and everywhere else. But the key constraints there aren’t housing density (although I do wonder if school density is lower in the outer suburbs?). They’re traffic and over-wrought perceptions of “stranger danger”.

All in all, the current levels of walking (2.1 per cent) and cycling (4.5 per cent) to work that apply to the inner suburbs seem like a reasonable, but ambitious, target for the outer suburbs, given that job density is higher in the inner suburbs.

As I’ve argued elsewhere, sprawl appears to have only a small independent effect on obesity. A recent study by Zhenxiang Zhao of the University of Illinois, Effects of Urban Sprawl on Obesity (PDF 485KB), examined data on 53 large metropolitan areas using a methodology designed to minimise selection effects. The author concludes that “overall, my results suggest that urban sprawl did cause an increase in obesity, but its effect was relatively modest … a 1% decrease in the proportion of the population living in dense areas increased the prevalence of obesity by 0.1% to 0.2%”.

Sprawl has its downsides but over-egging the pudding doesn’t help rational debate.