Disparities in daily walking patterns are a strong predictor of obesity prevalence across countries, according to recent research out of Stanford (Calif.) University.
The researchers used data from smartphones with built-in accelerometry — which counts a user's daily steps — to analyze physical activity for 717,527 people in 111 countries. Researchers determined there is widespread "activity inequality" within countries, noting, "inequality in how activity is distributed within countries … is a better predictor of obesity prevalence in the population than average activity volume," according to their paper, published in Nature.
Their findings suggested people in countries with lower levels of obesity tended to engage in similar levels of physical exercise each day. However, in countries with greater disparities in the amount of exercise people engaged in each day, the rate of obesity was higher. "For instance, Sweden had one of the smallest gaps between activity rich and activity poor," said Tim Althoff, a doctoral candidate in computer science at Stanford and first author on the paper. "It also had one of the lowest rates of obesity."
The analysis revealed the U.S. ranked the fourth worst country in activity inequality, reflecting its high level of obesity. Within the U.S., the researchers also analyzed data on "pedestrian-friendly" cities and found participants in more walkable cities reported greater physical activity across age, gender and body mass index groups.
"Our findings have implications for global public health policy and urban planning and highlight the role of activity inequality and the built environment in improving physical activity and health," the study authors concluded.