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Taking steps to learn more about obesity with smartphones

Many of my friends use smartphones to track their steps as they walk about town to grocery shop, grab lunch or just take a break from the computer. Their daily goal is typically 10,000 steps. Now researchers are using this type of data to study public health.

Stanford researchers used step data captured by smart phones to analyze the activity levels of more than 700,000 men and women from 111 countries during a 3-month period. Although the data was anonymized, it included key health demographics such as age, gender, height and weight so the research team could calculate each person’s body mass index.

The investigators' goal was to figure out why obesity is a bigger health problem in some countries than others. As outlined in a paper in Nature, they found that people walked a similar amount each day in countries with little obesity, whereas there was a big activity gap in countries with high levels of obesity — and they dubbed this 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 Scott Delp, PhD, a Stanford professor of bioengineering and of mechanical engineering, in a Stanford news release.

Delp and his colleagues also found a gap in activity levels between genders — men walked more than women — that varied from country to country. Overall, their research identified strong correlations between activity inequality, the gender-activity gap and obesity levels.

How did the United States rank? It was ranked near the bottom for activity inequality due to a large gap between the activity rich and activity poor. It also has a large gender-activity gap and high levels of obesity.

The researchers hope their results will inspire designers to make cities more walkable and pedestrian-friendly. “In cities that are more walkable everyone tends to take more daily steps, whether male or female, young or old, healthy weight or obese,” explained Jennifer Hicks, PhD, director of data science for Stanford's Mobilize Center.

Previously: “We should act now”: Stanford expert calls for more targeted anti-obesity policies and Can a food-tracking app help promote healthy eating habits?
Photo by Petr Kratochvil

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