Monday, January 31, 2011

Orderly neighbourhoods with lots of green space good for the waistline?

Aesthetics of the residential environment is important for sustainability and even for obesity prevention as I alluded to in my introduction of sustainability on January 21st. I hesitantly categorized my discussion of ‘sustainability’ and how that relates to obesity into four separate posts, but you will find that the categories tend to blur together. Please keep that in mind as you read all posts in the series.

It’s probably a no-brainer that if your neighbourhood were to look like a dump, you would be less likely to be out and about being active. Well, the scientific literature is starting to catch up with common sense. Studies are finding that the presence of a lot of garbage, graffiti, derelict buildings, etc, in a neighbourhood tend to dissuade people from being physically active, and can actually increase their chances of being obese (1-3). There are a few explanations for why this might be; an obvious one is that if there is nothing interesting to look at, residents may not be enticed to go for a walk, or run, or use active transportation to get somewhere.  A run-down neighbourhood may also be perceived as dangerous, or may invite crime (perhaps you have heard of the ‘broken windows hypothesis’?) and actually be dangerous (4). This may prevent adult residents partaking in physical activity outside, and make moms leery of letting their children play outside.

Photo credit: W. Murphy

Stress can also result from living in a hazardous environment – stress has been shown to have direct effects on metabolism, and has been linked to obesity (2,5). Eating may also be used as a coping strategy for stress (6,7). Who hasn’t taken the Haagen Daas out after a stressful day at work? If you’re constantly stressed and have crappy, cheap food nearby that makes you happy, well then it’s not hard to overeat.

Dilapidated neighbourhoods likely do not have as many community residents looking out for their interests as say the Bridle Path in Toronto, the Glebe in Ottawa, or the Shaughnessy neighbourhood in West Vancouver.  These less cared for neighbourhoods, therefore, are prone to further environmental injustices such as illegal dumping.

I think, in addition to neighbourhoods that are not well cared for, we must also consider the mind-numbing monotony of suburban design. If I did not have a dog that did not require a walk two times a day, I would never walk around my neighbourhood just to ‘go for a walk.’  EVERYTHING LOOKS THE SAME!

Nearby greenery may also be important for the promotion of physical activity and prevention of obesity (I recently twittered about a new way to measure the quality of open space in neighbourhoods using Google Earth – Come, to think of it that may end up being my last PhD thesis paper…)  A study that used data from eight different European countries found that living in an area with a lot of greenery (objectively measured) increased the odds of adult residents participating in physical activity by quite a large amount (3.32-fold to be exact), compared to low greenery areas (8). High greenery areas also reduced the odds of obesity by 40%.  Associations among children are similar but less strong than they are in adults (9,10). 

Perceived greenery on the other hand, may be more important than objectively measured greenery; for instance, one study found an association between walking trips per month and the amount of greenery residents perceived, but not with that measured by the researchers (11). Population density may also be important as some studies have shown that greenery is not important in rural areas (12) or areas where other amenities are not that easily accessible on foot (11).

Photo credit: F. Grammenos
In addition to obesity prevention, greenery is beneficial for overall well-being. A study conducted in the UK found that people who were more dissatisfied with the green spaces in their neighbourhood were more likely to score lower on the mental health and vitality scales of the SF-36, than those who were not dissatisfied (13). Cognitive function has even been shown to improve among low-income children when they are provided with window views of greenery, in contrast to paved or bare dirt surfaces(14). Interestingly enough, a cross-Canada run is now underway to get Canadian children outside to play and learn - go Colin!  

In summary, if we like the way our neighbourhoods look we may be more likely to be physically active and less likely to be obese. Neighbourhoods that are cared for and regularly used are more sustainable, and more greenery can help to recycle the harmful outputs of urban/suburban living.   



References


  1. Grafova IB. Overweight children: Assessing the contribution of the built environment. Preventive Medicine. 2008; 47(3): 304-8 
  2. Stafford M, et al. Pathways to obesity: Identifying local, modifiable determinants of physical activity and diet. Social Science & Medicine. 2007; 62: 1882-97 
  3. Saelens BE & Handy SL. Built environment correlates of walking: A review. Medicine & Science in Sport Exercise. 2008; 40(7S): S550-66 
  4. Macintyre S. et al. Place effects on health: How can we conceptualise, operationalise, and measure them? Social Science & Medicine. 2002; 55(1): 125-39 
  5. McEwen BS. Protective and damaging effects of stress mediators. New England Journal of Medicine 1998;338(3):171-9. 
  6. Kumanyika SK. Environmental influences on childhood obesity: ethnic and cultural influences in context. Physiology & Behavior 2008;94(1):61-70. 
  7. Rosenkranz RR, Dzewaltowski DA. Model of the home food environment pertaining to childhood obesity. Nutrition Reviews 2008;66(3):123-40. 
  8. Ellaway A. et al. Graffiti, greenery, and obesity in adults: secondary analysis of European cross sectional survey. BMJ. 2005; 331:611-2 
  9. Bell JF et al. Neighborhood greenness and 2-year changes in body mass index of children and youth. American Journal of Preventive Medicine 2008;35(6):547-53 
  10. Wheeler BW et al. Greenspace and children’s physical activity: A GPS/GIS analysis of the PEACH project 
  11. Tilt JH et al. Using objective and subjective measures of neighbourhood greenness and accessible destinations for understanding walking trips and BMI in Seattle, Washington. American Journal of Health Promotion. 2007; 21(4): 371-79 
  12. Liu GC et al. Green neighborhoods, food retail and childhood overweight: differences by population density. American Journal of Health Promotion 2007;21(4 Suppl):317-25. 
  13. Guite HF, Clark C, Ackrill G. The impact of the physical and urban environment on mental well-being. Public Health 2006;120(12):1117-26. 
  14. Wells NM. At home with nature: effects of "greenness"on children's cognitive functioning. Environmental Behavior 2000;32(6):775-95.