Body weight is a very personal thing. Some people want to weigh less, and others want to weigh more. In general, however, most people want to lose weight; many countries have populations that on average are overweight. There can be additional healthcare expenses and other costs associated with obesity, which is why health professionals are interested in understanding body weight trends for populations as a whole.

Researchers at Stanford University have uncovered some interesting data that could help understand the differences between different groups of people when it comes to obesity. They performed a global study of the average number of steps taken by owners of smartphones. They analyzed results from 717,000 people from 111 countries, for an average of 95 days per subject. They discovered that “activity inequality” is a prime predictor of population obesity. For example, Sweden had the smallest gap between those who had the most steps per day, and those who had the least. And it has one of the lowest rates of obesity. On the other hand, the U.S. has a much larger gap between the most and least active subjects, ranking fourth from the bottom in terms of activity gap. And the U.S. has high levels of obesity. The researchers also found that urban design plays a role. Cities that are more conducive to walking tend to have a much smaller activity inequality gap among their populations.

At a higher level, this study also illustrates the rich potential of smartphones as a data collection tool for population research. The wealth of sensors that they contain and the high degree of market penetration worldwide makes them an easily accessed source of data for analysis. As we continue to develop new wearable devices to track biometric data, it’s important to keep in mind that we may already have relevant devices in our pockets.