This week’s Journal of the American Medical Association has and article that shows that in Ontario, Canada, neighborhoods with higher walkability scores were associated with a decreased prevalence of overweight and obesity and diabetes between 2001 and 2012. (1) That means that exercise cures obesity, right? No. They also showed that there wasn’t actually any increase in physical activity when there was a higher walkability score so “further research is necessary to assess whether the observed associations are causal.”
We already know from close, careful studies, that when you directly use exercise you cannot lower weight; so if a study using a complicated, multi-step, multi-supposition connection between exercise and lower obesity there must be a different explanation.
What’s the walkability index? The walkability index was derived from 4 equally weighted parts: population density (number of persons per square kilometer), residential density (number of occupied residential dwellings per square kilometer), walkable destinations (number of libraries, banks, stores… within a 10 minute walk), and street connectivity (number of intersections with at least 3 converging roads or pathways). Canadian census data has this kind of information for “dissemination areas,” the smallest geographical units, consisting of between 400 and 700 persons. The walkability scores ranged from 0 to 100 for 8777 dissemnination areas, and included 15 municipalities with a combined population of more than 7 million residents of Southern Ontario Province.
At the beginning of the time window in 2001, the prevalence of overweight and obesity was already less in the highest quintile of walkability score areas versus the lowest,
(43% vs 54%). Between 2001 and 2012, the prevalence of overweight and obesity increased in less walkable neighborhoods but did not change as much in the higher walkability ones. Rates of walking or cycling and public transit use were higher when walkability was higher but leisure-time physical activity, diet and smoking did not vary by walkabilty and did not change over time.
So how does this work and can we cure obesity by making everwhere more walkable – AKA make more exercise? An accompanying editorial points out some of the problems of this conclusion. (2) If you jump to the not unreasonable conclusion that “walkable urban design” means “more exercise” then the title of this editorial “Can walkable urban design play a role in reducing the incidence of obesity-related conditions?” is true. If you say that exercise reduces obesity as opposed to “obesity-related conditions” then not so true. But maybe the end -building more walkable environments, justifies the means -lying that exercise fixes obesity.
At any rate I am a big supporter of Connex, (http://connexmoves.org/) a non-profit group dedicated to the development of activity routes throughout Portsmouth and the surrounding community.
1. Creatore MI, et al. Association of neighborhood walkability with change in overweight, obesity, and diabetes. JAMA. 2016;315:2211-20.
2. Rundle AG, Heymsfield SB. Can walkable urban design play a role in reducing the incidence of obesity-related conditions? JAMA. 2016;315:2175-7.
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