At a number of recent city events I heard several people mention the obesity problem facing our kids.
Diabetes and obesity is a problem for our nation, but the problem is unevenly distributed geographically and socioeconomically. Darker colors in the map below indicate greater obesity. There are lower levels of obesity in coastal California.
Understanding mechanisms (ie causes) related to natural phenomenon is tough without access to good experimental data. Observational data are useful in helping describe patterns and identifying associations.
Correlation doesn't equal causation. Correlation can help test ideas about mechanisms, but there is nothing better than good ol' experimental data to cleanly demonstrate causation. Check out this next map. The lack of an automobile and distance to a supermarket is spatially correlated with obesity.
Maybe we should fund a study that gives people cars and see if that results in an improvement in their obesity? Automobiles could be a solution to obesity. Well, maybe not.
On the other side, I've reviewed several epidemiological studies of obesity and urban design that are based on observational associations (correlations). Even for an observational study, the conclusions that could be drawn were fairly thin, however they were exciting because they pointed toward public policies that don't require direct intervention at the patient level. However, there were still too many alternative explanations that can explain the patterns seen in those studies, that had not been strongly tested. This doesn't mean the authors were barking up the wrong tree, only that we can't yet see clearly what climbed out on a limb.
Fortunately for our local kids, the issue is less pressing than in other areas of the country. Our kids have a relatively low level of obesity. Here are some data from last year's California Healthy Kids Survey. These BMI distributions are from our local high schools.
There are lots of cool reasons, which I support, for improving our infrastructure. Doing it because we want to keep our kids from becoming obese is not as strong a justification as others.