In sum, they found that inequality among locales in terms of how likely it is for people to walk, correlates directly to obesity levels. Notably, the data don't vary much according to income or gender (although men do tend to walk more than women). The key factor is a city's walkability.

Our largest and oldest cities, such as New York and Boston, are most walkable and offer the lowest activity inequality. Even hilly San Francisco, because of its layout, ranks much better than nearby San Jose.

Among the least walkable were several cities in Texas, including Fort Worth and the Dallas suburb of Arlington.

Globally, the U.S. ranked poorly in terms of activity inequality. Sweden, for example, had very low inequality and, correspondingly, one of the lowest rates of obesity.

Another study, by the Centers for Disease Control and Prevention, identified what’s called a "sprawl index," based on population density. In general, the more densely packed a community’s population the more fit and slender its residents tend to be. To some this seems counterintuitive, since many of us gravitate to wide open spaces in pursuit of more healthful outdoor activities. Yet, urban walking appears to do the most people the most good.

To underscore the importance of their research, the people at Stanford have estimated that 5.3 million deaths per year in the U.S. are "associated" with inactivity. No doubt. Obesity is a growing problem and, clearly, increased activity helps reduce obesity.

The research covered nearly three-quarters of a million people in 111 countries, using smartphones that measured activity. As a result, the study seems likely to have under-reported poorer people, although the data were consistent among income levels that were measured.

Indeed, the study shows that in more walkable cities activity is greater throughout the day and throughout the week, across age, gender, and body mass index groups.

In some ways, the study begs the obvious: walking is good. But drilling down, the researchers believe that city planning—designing urban centers in ways that facilitate walking—would be an important, yet relatively inexpensive way to combat obesity.

According to the researchers, "the findings have implications for global public health policy and urban planning and highlight the role of activity inequality and the built environment for improving physical activity and health."

Building more walkable cities would be a step in the right direction.

(c) Peter Funt. Distributed by Cagle syndicate.