Double Your Converse

Who Knows Why Obesity Doubled?

Speculation abounds alongside some (unsubstantiated) convictions about why obesity doubled over the last few decades. So it’s refreshing to read an objective analysis from a new perspective on the subject. In Review of the Economics of the Household, Charles Baum and Shin-Yi Chou take on the question in a methodical, quantitative way, as economists are wont to do.

They use longitudinal survey data spanning two decades to estimate the effect of a wide range of social and environmental factors on obesity prevalence. They find indications that SNAP (food stamp) participation, cigarette smoking, and urban sprawl have small, consistent impacts. But in aggregate, they find that a large collection of factors — all proposed by others to be driving obesity rates up — could not explain more than 6.5% of the changes in obesity rates observed over the two decades they studied.

They also find little evidence that common proposals for reducing obesity — e.g., food taxes, restaurant regulation, urban planning — would have substantial effects.

Perhaps we have a bit of Male Answer Syndrome at work in our feeble attempts to understand obesity. You know you’ve encountered it. Men are especially overconfident when wrong. Likewise, people with the greatest confidence in their answers for obesity are often especially ignorant about the condition.

In a classic commentary, the eminent epidemiologist Geoffrey Rose reflected on the tension between caring for the health of individuals and the population:

The two approaches are not usually in competition, but the prior concern should always be to discover and control the causes of incidence.

We must, then, deepen our commitment to understanding the processes that are driving an excess of obesity. Ready, fire, aim isn’t working too well.

Click here for the study by Baum and Chou. Click here for further perspective from PLOS Blogs. Click here for the commentary by Rose.

Double Your Converse, photograph © Orangeya / flickr

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4 Responses to “Who Knows Why Obesity Doubled?”

  1. June 14, 2015 at 7:42 am, Joe Gitchell said:

    Complexity is tough…defies easy pattern recognition.

    But we can’t stop trying!

    Thanks, Ted. I particularly like knowing that I can self-diagnose MAS–chronic, relapsing, with acute outbreaks, I’d say!


    • June 14, 2015 at 4:41 pm, Ted said:

      Thanks, Joe!

  2. June 14, 2015 at 8:32 am, Mary-Jo said:

    Perhaps if for every new case reported, a method is devised to back-track factors leading up to it, and this information is documented — maybe in a couple years, the data could be analyzed to determine most prominent factors contributing to incidence. I vaguely remember a paper by Swinburn and Egger awhile back (BMJ. 1997 Aug 23;315(7106):477-80.An “ecological” approach to the obesity pandemic. Egger G, Swinburn B.) that was great about elucidating the various factors associated, but it sought to find a way to establish the main driving forces, mediators, and outliers. If, somehow, that system or a similar one could be made more practical, maybe we could figure out why occurrence happens per each case and, then, on a larger scale. Just an idea.

    • June 14, 2015 at 4:40 pm, Ted said:

      Thanks, Mary-Jo. I think a key ingredient to sorting this out will be curiosity. I run into lots of people with Male Answer Syndrome when it comes to obesity. Not much curiosity about obesity in many people.