A worldwide study has found that countries with large differences in walking rates in their citizens have higher obesity levels than those who do not see such a vast spread.

The United States also did not fare well, ranking in the bottom half of nations studied with 4,774 steps taken each day, or below the global average of 4,961 steps.

Activity Inequality

The study, where Stanford researchers used smartphones to track activity levels for 95 days on average, comprised 717,000 individuals in 111 countries.

The team dubbed the phenomenon “activity inequality.”

“If you think about some people in a country as ‘activity rich’ and others as ‘activity poor,’ the size of the gap between them is a strong indicator of obesity levels in that society,” said co-lead author and bioengineer Scott Delp in a statement.

The United States emerged as fourth from the bottom in activity inequality, noting a massive gap between activity rich and activity poor. It also had high obesity levels, the team found.

Compare this with Sweden, which had one of the smallest gaps between the most and least active citizens, and also had among the lowest obesity rates in the world.

The team equipped smartphones with small sensors called accelerometers to automatically record participants’ stepping motions. Data were obtained from the Azumio Argus app, which monitors physical activity as well as other health behaviors.

The app kept the data anonymous but provided age, gender, weight, and height.

Gender Gap, Promoting Walkable Cities

In addition, the researchers saw gender as a significant factor in per-country difference. Not unlike what previous studies found, males walked more than females, with outcomes related to this gender gap varying from one nation to another.

At the peak of activity inequality, women’s activity is decreased “much more dramatically” than that of men, with the negative links to obesity potentially affecting women more, explained co-leader and computer scientist Jure Leskovec.

To better analyze the causes and effects of activity inequality in urban locations, the researchers also correlated the so-called walkability index to smartphone activity data. This probed how the environments of 69 U.S. cities tied up with activity, obesity, and overall health.

The results showed that cities most conducive to walking maintained the lowest activity inequality. Walkable cities see its residents taking more everyday steps, whether they are male or female, young or old, or healthy-weight or obese.

The hope is for the data to help design towns and cities to encourage people to be more physically active.