Neighborhood Walkability and Body Mass Index: Important in Men

Public health officials across the globe are seeing a reciprocal relationship of obvious concern: obesity is increasing and physical activity is decreasing.

Obesity, now an epidemic, is prompting public health professionals to research social and environmental causes.

The May 2016 issue of the American Journal of Public Health included a study that assessed how living in a walkable neighborhood affected Canadians' body mass indexes (BMI). These researchers, based at McGill University in Montreal, used data from Canada’s National Population Health Survey (NPHS, a biannual study that began in 1994-1995).

The researchers took data from the first seven cycles of the NPHS study, which covered periods from 1994-1995 to 2006-2007. They analyzed data from adults 18-55 years old (n=2935) who lived in urban areas and had reported their heights and weights.

Researchers excluded adults who weighed less than 77.1 pounds (35 kilograms) and pregnant women.

Researchers selected BMI as the main outcome, and they assessed walkability based on the participant’s neighborhood’s walk score. Walk score is determined based on distances to certain amenities (e.g. restaurants, parks, schools, etc.). The researchers divided the walk score (ranging from 0-100) into four quartiles (ranging from low-walkable neighborhoods to high-walkable neighborhoods).

Results showed neighborhood walkability had no influence on women’s BMI.

However, researchers did see an influence on men’s BMIs. Living in neighborhoods in the highest quartile for walkability was associated with the lowest BMIs in men.

Moving from low-walkability neighborhoods to higher walkability neighborhoods reduced BMI by approximately 1 kg/m² (which translates to 3 kg or 6.6 pounds for the average man). Men who moved to neighborhood designated low walkability increased their BMI by approximately 0.45 kg/m².

An unexplained and unexpected finding was that neighborhoods in the second Walk Score quartile neighborhoods (those slightly less walkable than the most walkable neighborhoods) had the most unfavorable BMI trajectories. One would expect to see the most unfavorable BMI trajectories in the least-walkable neighborhoods.

The researchers propose that the least-walkable neighborhoods may have well-developed public transportation systems that encourage utilitarian walking.

The researchers concluded that policy makers and urban planners need information about the precise mix of physical and social neighborhood attributes that are associated with reductions in body weight. Having that knowledge would help identify environmental modifications that promote health policy.