A new study from Stanford University used smartphone data to track down activity levels of people around the globe. Smartphones have tiny sensors called accelerometers that can record stepping motions. Using data from an app called Azumio Argus, which records physical activity, they were able to map exercise patterns in more than 100 countries.

The researchers found that in countries where obesity levels are relatively low, people walked similar amounts per day.

Image credit: The Simpsons / Mind of a Winner
Image credit: The Simpsons / Mind of a Winner

However, they also found that in countries where there were significant gaps between people who walked a lot and people who walked very little a day, those countries showed higher rates of obesity. The findings were published in Nature this week.

Activity inequality showed which countries are ‘activity rich’ or ‘activity poor’

The Azumio Argus app provided anonymized data to the researchers but gave them key demographics that were needed for the study: gender, age, height, and weight. Using the two latter demographics they were able to calculate each individual’s body mass index.

Over 5.3 million people die each year from causes associated with physical activity, such as obesity, heart disease, and diabetes. For the study, the research team used data taken from smartphones to track down physical activity habits of 717,000 men and women from 111 countries. Their steps were analyzed for about 95 days.

The team named the phenomenon “activity inequality,” which evokes the concept of income 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 Scott Delp, a bioengineers and co-author of the new study, according to Stanford University News.

The authors also noted that gender also had a major effect on activity inequality. In the United States, for instance, other studies found that men walk more than women overall.

But Delp and his colleagues found the gender gap varied drastically from country to country and almost every time had adverse consequences for women.

Over 5.3 million people die each year from causes associated with physical activity, such as obesity, heart disease, and diabetes. Images credit: WHO
Over 5.3 million people die each year from causes associated with physical activity, such as obesity, heart disease, and diabetes. Images credit: WHO

“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,” said Jure Leskovec, a computer scientist at Stanford University and lead author of the study.

More than a third of Americans are obese

The researchers noted the study relied more on data from 46 countries for which the Azumio app provided over a thousand anonymous users, which proved to be enough to form the foundations of the analysis.

The researchers found a significant correlation between activity inequality, obesity levels, and the gender-activity gap.

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

However, the results weren’t as good in the United States. The U.S. ranked fourth from the bottom in activity inequality, which indicates a significant gap between activity rich and activity poor and ranked fifth from the lower part of the gender step gap.

Image credit: NCSL
Image credit: NCSL

According to the Centers for Disease Control and Prevention, more than one-third (36.5 percent) of American adults have obesity. Out of that percentage, non-Hispanic black people have the highest rates of obesity, at 48.1 percent. They are closely followed by Hispanics, at 42.5 percent, non-Hispanic whites with 34.5 percent, and non-Hispanic Asians with 11.7 percent.

The CDC says that obesity is higher among middle age adults aged between 40 and 59 years old (40.2 percent), and people aged 60 years or higher (37 percent). Young adults, or people ages 20 to 39, have the lowest obesity rates, at 32.3 percent.

Obesity is also directly correlated with income inequality. For instance, the CDC notes that among non-Hispanic blacks and Mexican-American men, those with higher incomes are more likely to suffer from obesity. However, higher income women are less likely to be obese compared to low-income women.

City designs directly impact walking patterns among Americans

The researchers also took a closer look at how the built environment of 69 U.S. cities related to activity inequality. They found that city design does impact the health of people living in them, as cities that were most conducive to walking had lower rates of activity inequality.

For example, they analyzed data from three California cities –San Francisco, San Jose, and Fremont- and they determined that San Francisco had the highest walkability rates and the lowest levels of activity inequality. According to Jennifer Hicks, director of data science for the Mobilize Center at Stanford, in cities that are more walkable, both men and women tend to take more steps, regardless of their age or their weight.

The research team now hopes to utilize the same methodology to push their research further. They expect to use appropriate apps and sensors to link activity within and across populations with food intake, or analyze how activity and inactivity affect mental health.

Source: Stanford University News