Researchers from Stanford University have utilized smartphones to track activity levels in 700,000 people from 111 countries to possibly identify a correlation between number of steps, environment and obesity rates.

The study, published in Nature, used pedometer sensors to measure activity rates globally and identify differing obesity rates by country. Led by Jure Leskovec, a computer scientist, and bioengineer Scott Delp, the study coined the term “activity inequality” to explain the difference in activity levels and its effect on a nation's obesity rate.

"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," Delp said.

Using the Azumio Argus application, which tracks activity, researchers provided data on age, gender height and weight. Data was taken from 46 countries that provided at least 1,000 participants to outline the correlation in activity inequality, gender-activity gap and obesity rates.

"For instance, Sweden had one of the smallest gaps between activity rich and activity poor, and the smallest disparity between male and female steps," said Tim Althoff, a doctoral candidate in computer science and first author. "It also had one of the lowest rates of obesity."

In nations where the gender-activity gap was larger, women were more prone to higher levels of obesity.

"When activity inequality is greatest, women's activity is reduced much more dramatically than men's activity, and thus the negative connections to obesity can affect women more greatly," Leskovec said.

When analyzing the environments of 69 U.S. cities, researchers found that the more “walkable” the city, the less activity inequality was found.

"Looking at three California cities in close geographic proximity—San Francisco, San Jose and Fremont—we determined that San Francisco had both the highest walkability score and the lowest level of activity inequality," said Jennifer Hicks, director of data science for the Mobilize Center at Stanford. "In cities that are more walkable everyone tends to take more daily steps, whether male or female, young or old, healthy weight or obese."