Tuesday, November 7, 2017

Density And Obesity

http://www.citylab.com; October 11, 2017


Hello Everyone:

Big day in Virginia, New Jersey, and other states holding elections.  If you have any questions about where to vote or need information about registering to vote for next year's mid-term elections, please check out vote.org.  Thanks. On to today's subject: obesity in the suburbs.

Here is a fact about urban life: "Living in a more densely built area significantly lowers your risk of obesity."  This statement is how Feargus O'Sullivan opens his CityLab article "Obesity Thrives in the Suburbs."  This inevitable conclusion is supported in a new survey of British cities which compares the obesity rates with housing density.  The study, Association between adiposity outcomes and residential density: a full-data, cross-sectional analysis of 419562 UK Biobank adult participants co-authored by Dr. Chimney Sarkar, PhD; Prof. Chris Webster, DSc; Prof. John Gallacher, PhD, published in the British medical journal The Lancet (thelancet.org; date accessed Nov. 7, 2017), sponsored by the University of Hong Kong, UK Biobank, and the U.K. Economic & Social Research Council, concluded that "obesity rates were markedly lower in areas where homes were more tightly clustered."

Mr. O'Sullivan concedes the obvious health benefits of walkable communities (citylab.com; Dec.11, 2014; date accessed Nov. 7, 2017).  However, what makes The Lancet article, first reported by Reuters (uk.reuters.com; Oct. 5, 2017; date accessed Nov. , 2017), truly landmark is its sheer scale, assembling data from 419,562 respondents in 22 British metropolitan areas over a four year period.  Mr. O'Sullivan writes, "While it would be mistaken to assume that observations made in the U.K. could apply everywhere, they make one thing clear: Residents' health is highly likely to improve when sprawling suburbs are made more dense."  Mr. O'Sullivan reproduced a graph, reprinted from The Lancet Planetary Health (sciencedirect.com; October 2017; date accessed Nov. 7, 2017) charts the levels of obesity in relation to specific rates of housing density.

The graph's three tables track: Body Mass Index, waist circumference, and whole body fat compared to housing density for a particular neighborhood.  The co-authors controlled for age and gender, thus, for example, young women living in less dense and dense areas were directly compared instead of being measured against people from other areas.

Feargus O'Sullivan reports, "The worst obesity rates, the study finds, are among British people who live with 1,800 homes per square kilometer (4,662 dwellings per square mile)."  This pencils out to nearly "the typical density for London's more sprawling,low-density outer boroughs, whose average density of 1,590 dwellings per square kilometer (data.london.gov.uk; date accessed Nov. 7, 2017) is brought down by the large areas of parkland and small areas of farmland still within the city limits."  The below this density rate, obesity rates start to drop, "the study finding that the lack of walkability for British people living in sparsely populated areas was compensated for by a relatively active lifestyle."

But people who live in very sparsely populated communities still exhibited greater rates of obesity than people who lived in more dense cities.  The cut-off point is around 3,200 dwellings per square kilometer, greater than that, residents presented consistently lower levels of obesity than their  counterparts in less dense communities (in an aside, Mr. O'Sullivan writes, "The U.K. currently recommends this level of density for all newly built districts.").

Further up the density scale, people residing in higher densities, typically inner London ("which has an average of 4,500 dwellings per square kilometer"), have markedly lower average BMI, whole body fate, and waist measurements, a clear indication of a health advantage over residents living in more sprawling lay developments in Great Britain.

This begs the question, "...why is obesity less common in densely built areas?"  The obvious reason is greater walkability than less dense areas.  Think about for a minute. Look around where you live and see how close or far the nearest coffee place is to you where you live.  If you live in a densely built area, chances are the nearest coffee place (places) is within short walking distance.  Also, highly dense areas have de-incentivize driving to reduce congestion and free up more pedestrian thoroughfares.  The city of Oslo, Norway announced that it was banning all cars from its city center by 2019 (businessinsider.com; Aug. 5, 2017; date accessed Nov. 7, 2017).  The study co-authors offer another reason.

A highly compact dense residential environment might act as a proxy for enhanced community social capital and support...The intangible stress-relieving potential centrality, accessibility, and social capital needs to be further examined in view of their protective effects on obesity.

The co-authors can start by reading contemporary urban planning and design godmother Jane Jacobs' book Death and Life of Great American Cities, which sang the praises of walkability.  However, you do not have to be an urban designer or a university researcher to understand that being at the center of things, being able to easily get around, having more opportunities to create a wider social network-without using the social network-might make you less stressful, encourage to shut down your device and leave the house.  Imagine that!

Feargus O'Sullivan marvels at the study's size and findings, "Despite its impressive size, the study's findings have some potential limits to their relevance that the authors themselves acknowledge."  One of the limits of the study's relevance is people how prefer a sedentary life.  Individuals who prefer a slower pace lifestyle choose to move to a less dense area.  Mr. O'Sullivan reports, "The study counterbalanced this hypothesis by comparing obesity levels among newly arrived suburbanites and long-term residents.  They found found no difference between the two groups, implying (but, vitally, not proving) that the suburbs were not attracting people more prone to obesity."

Another limit is the fascinating question left unanswered: "Is there an upward limit after which home density becomes so great that it actually encourages obesity?"  It sounds like a strange question but the study found no upward limit, however the it only used data from the United Kingdom where densities never reach the extremely numbers of some cities in South and East Asia.  This would be a good way to expand the study: look at density and obesity in South and East Asia, as well as other cities in Africa, Europe, and North America.

Association between adiposity outcomes and residential density: a full-data, cross-sectional analysis of 419562 UK Biobank adult participants makes important assertions.  "If obesity drops as homes cluster more closely together, there is a clear public health argument for densifying the suburbs, providing that densification is mixed-used and thus also comes with a denser cluster of shopping,entertainment, and other amenities that make walking desirable."

Presently, the "recommended density for new development of housing in the U.K. of 3,200 homes per square kilometer might ensure that future neighborhoods will have a layout somewhat less conducive to high obesity,..."  The majority of British suburbanites, nevertheless, continue to live in areas where considerably lower density is encased in amber by local planning ordinances and resistance from local residents who fear drops in property values or congestion.  Another possibility is the understanding "that these environments are not especially healthy permeates through society,..." Britain's low-density neighborhoods might prove a more hospitable target for future residential development the nation so desperately needs.  

Perhaps, American residential developers could take a few lessons from Association between adiposity outcomes and residential density: a full-data, cross-sectional analysis of 419562 UK Biobank adult participants.