Wednesday, February 01, 2012

Obesity in Women Linked to Living Near Parks?!

If you like your data clean, pretty and predictable, you probably don't want to read the rest of this post.

Researchers from my hometown here in Ottawa recently published a study ahead of print in the journal Obesity. The paper, Relationships Between Neighborhoods, Physical Activity, and Obesity: A Multilevel Analysis of a Large Canadian City looked at a number of different built environment variables and their impacts upon the probability of both leisure time physical activity and overweight and obesity in the population.

The statistical models controlled for: Age, education, household income, smoking status, and, given we live in a city where there's a lot of snow, season of data collection.

The variables that were considered as potential neighborhood based influencers of physical activity and obesity were: Total bike and walking path length, number of free or minimally expensive indoor and outdoor recreational facilities, park area and green space, social cohesion, neighbourhood safety, number of grocery stores, fast food chains, convenience stores, specialty food stores and full service restaurants.

The findings?

In men, almost nothing mattered. In fact with weight, nothing at all mattered. Number of fast food joints, convenience stores, grocery stores, park space or recreational facilities - none of these things seemed to impact upon a man's weight. There was however one variable that correlated with increased physical activity. Crime rate. Yup, the more dangerous the neighbourhood, the more active the man, to the tune of a 14% increase in their odds of being physically active for every standard deviation increase in crime rate.   Running away from the bad guys?

In women? With women for every standard deviation increase in park area they were found to be 17% more likely to be physically active. So far so good, but check this, for every same standard deviation increase in park area women were also 15% more likely to be overweight or obese. In fact the increased risk to overweight and obesity seen with increasing park size in women was only ever so slightly eclipsed by the 17% increased risk conferred to their weights by a standard deviation increase in numbers of convenience stores.  The riskiest thing for women's weights according to this paper?  Fast food restaurants with a 38% increased risk of weight for every standard deviation increase in those. 

So what do these numbers mean? So many questions.  Should inactive men be encouraged to live in dangerous neighbourhoods? Does nothing in a man's environment really matter to their weights?  Should women rethink that new home they're considering beside the park?

I don't think so.

I think all these numbers mean is that the reasons why people gain weight and exercise, they're stupidly complicated and trying to suss out the impact of a dozen or two different criteria on this sort of ridiculous complexity, might in fact be turn out to be a bit of an exercise in statistically meaningful futility.

Prince, S., Kristjansson, E., Russell, K., Billette, J., Sawada, M., Ali, A., Tremblay, M., & Prud'homme, D. (2012). Relationships Between Neighborhoods, Physical Activity, and Obesity: A Multilevel Analysis of a Large Canadian City Obesity DOI: 10.1038/oby.2011.392

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  1. I'm thinking the women and the fast food findings are probably more to do with the convenience of not having to cook dinner especially after a long day at work. :)

  2. Anonymous12:44 pm

    It sounds to me like you think this information is useless.

    As the researchers note,I wonder if there could be some discussion about the directionality here - ie. do active women or overweight women choose to live closer to parks to support their lifestyle or goals? Or does their proximity to these spaces impact their activity and weight? Longitudinal data would sllow for information on causality to be identified.

    Neighbourhoods with higher crime may be more likely to be low income, so lower rates of obesity may be due to less access to healthy food or sufficient food, as well asl lower rates of vehicle ownership (meaning more walking or other modes of transport)

  3. Anonymous1:16 pm

    If you want to get more walking exercise, get yourself a dog! That's the only thing that gets me up and out walking at 5 am each morning! :)

  4. Anonymous1:19 pm

    I suspect that sex (male vs. female) is an inaccurate proxy for employment (which doesn’t appear in the list of variables controlled for). Although many women work outside the home, the people whose main occupation is raising kids at home are overwhelmingly more likely to be women than men.

    Let’s speculate a little further that people (mostly women) raising small children are more likely to live near a park (for the kids’ sake) than people employed outside the home and not parents of small children, but these same parents (especially mothers) of small kids are vulnerable to a lot of factors that may increase their weight, like lingering pregnancy weight, stress eating, reduced time to exercise, etc.

  5. If you're overweight you feel bad about yourself and likely choose to live near a park thinking you will get out more and lose weight but alas it's more complex than that.