Friday, February 18, 2011

Compact and diverse communities: sustainable and obesity preventive?

This is the third post in the series – ‘Sustainable community design and obesity prevention;’ only one more to go. Today I will obviously be discussing how compact and diverse areas can influence our waistlines. 

It makes sense that for neighbourhoods to be liveable (enjoyable, sustainable, useable, etc.) there must be interesting and necessary amenities accessible within easy walking distance.  Although there are differing views as to the meaning of ‘easy walking distance,’ I am referring here to destinations that are accessible in about 10 minutes or so – about 1 km, or the distance of a traditional city block.

These amenities should include banks, schools, restaurants/pubs, cafes, shopping, grocery and corner stores, parks and open spaces, and meeting places such as courtyards and piazzas.  The term ‘mixed land-use’ refers to the mixing of residential, commercial, and institutional uses. This makes neighbourhoods and the broader community more compact, as well as diverse. 

In an ideal world, I would live in an area where I could access all amenities, as well as my job, on foot.  Right now, according to www.walkscore.com, I live in a ‘car-dependent’ neighbourhood – scoring an abysmal 27/100. Curiously downtown Hull, QC (close to my home) seems to do pretty well, although I’m not convinced the site takes into account whether anyone actually lives there (e.g. downtown Hull is mostly government buildings).  In the better weather, I have to ‘force’ myself to bike the 12 km into work and back home.  Although I am no marathon runner, I consider myself to be in fairly decent shape, so assuming the average person would commute 24 km round trip by bike each day is not feasible (and I don’t even actively commute each and every day); obviously the walk is impossible and public transportation is a bit annoying.


Among adults, the general finding in the scientific literature is that mixed land-use, high density, and low sprawl (different measures that take into account density, degree of mixed land-use, block size, etc) are associated with increased walking (1), and a decreased probability of obesity (2) and high blood pressure among area residents (3). Mixed-use zoning alone can dramatically increase physical activity; a review of 12 studies showed that the median improvement in the level of physical activity was 161% (4).  In children, the association between compactness and weight is less clear and reflects, at least partly, a lack of similar studies with which to compare results (5).

The Centers for Disease Control and Prevention in the U.S. conducted a comprehensive review with the goal of developing recommendations for childhood obesity prevention at the community-level (6).  Included in the recommendations were:

  • Support for locating schools within easy walking distance of residential areas 
  • Zoning for mixed-use development

Compact, diverse neighbourhoods and communities are more liveable and likely more healthy, but can we afford to live in these places?  More people living in one area make amenities viable but that also increases land value.  How do we build or retrofit these communities, simultaneously making them profitable for developers/cities and equitable for all residents?  


References
  1. Saelens BE & Handy SL. Built environment correlates of walking: A review. Medicine & Science in Sport Exercise. 2008; 40(7S): S550-66 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2921187/ 
  2. Feng J et al. The built environment and obesity: A systematic review of the epidemiologic evidence. Health&Place. 2010; 16: 175-90 
  3. Leal C & Chaix B. The influence of geographic life environments on cardiometabolic risk factors: A systematic review, a methodological assessment and a research agenda. Obesity Reviews. 2010; March 1. 
  4. Heath GW et al. The effectiveness of urban design and land use and transport policies and practices to increase physical activity: A systematic review. Journal of Physical Activity and Health. 2006; 3 Suppl 1; S55-76  http://www.aapca3.org/resources/archival/060306/jpah.pdf 
  5. Carter MA & Dubois L. Neighbourhoods and child adiposity: A critical appraisal of the literature. Health&Place. 2010; 16: 616-28 
  6. Khan LK et al. Recommended Community Strategies and Measurements to Prevent Obesity in the United States. Morbidity and Mortality Weekly Report. 2009; 58(RR-7)  http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5807a1.htm