On average, people in the US take around the same number of steps daily as people in Mexico—about 4,700. But the US has a much higher obesity rate than Mexico—27.7 percent compared to 18.1 percent. Why?
The immediate and obvious answer is food culture, and that probably does play an important role. But a paper in Nature this week suggests something else we should be looking at: activity inequality. In the US, a small section of the population gets in lots of daily activity, dragging the average higher, but the majority of people get very little. Other countries, like Japan, are more equal: more people there tend to fall around the average.
Activity inequality is already part of the conversation about obesity. When we talk about problems like exercise deserts, we’re talking about how some groups of people live in situations where there aren’t many options for physical activity, leaving a portion of the population with below-average activity. A new look at global data, however, confirms that this is a vital way to analyze the problem: high activity inequality in a country means high obesity, much more reliably than low average-activity levels mean high obesity. And addressing this inequality specifically, rather than looking at average activity, could yield much greater results.