The street where you live could be making you fat. That’s what a study of 450,000 Americans suggests.

Ken Smith and colleagues at the University of Utah in Salt Lake City gleaned the height, weight and address details of people living in the Salt Lake City area from a database of drivers’ licences.

They then used census and map data to score neighbourhoods on various measures of “walkability”.

People with a lower body mass index – a measure of obesity – tended to live in areas with older buildings and where a higher proportion of people walked to work.


Building age is a factor in Salt Lake City, Smith says, because older houses tend to be surrounded by sidewalks, trees and shade, and close to shops, making it “easy and pleasant” to walk compared to newer neighbourhoods. “Older homes were built with pedestrians in mind.”

The average difference in BMI between the top and bottom 25% of neighbourhoods was 1.28 for men – equating to 4.5 kilos for someone 1.83 metres tall – and 0.95 for women, or 3 kilos for someone 1.65 metres tall.

Making cities more walkable won’t necessarily keep people in trim, however, as they may choose areas to suit their behaviour, rather than vice versa, he says.

“If it’s truly all selection, changing the environment is just going to induce a kind of migration,” Smith says.

Journal reference: American Journal of Preventive Medicine (DOI: 10.1016/j.amepre.2008.05.028)