In a recently published article in Nature magazine, researchers used smart phone data to track the activity of 717,527 people over the course of 68 million days in 111 countries. Some of their findings made obvious sense, but other discoveries were subtle, useful, and unexpected.

First, some general stats from the study:

  • Overall, the subjects in the study averaged 4,961 steps every day.
  • The country lowest in steps was Indonesia at 3,513 steps per day.
  • The highest was China, at 6,880 steps.
  • The United States was 4,774, slightly below average.

1. Activity Inequality

 Now, steps did correlate with national obesity rates, but not as strongly as the variation in walking, i.e. activity inequalityThe countries that had more variation in the number of steps their people took daily had a higher national rate of obesity. 

In this respect, America was the fourth worst country in regards to activity inequality, which could help to explain our obesity epidemic. This insinuates that, even if two countries had the same overall average number of daily steps, the country with more activity inequality would have more obesity due to more obesity in the less active portion of their population.

Or, to put it simply: variation in walking nationwide = higher overall obesity rates

2. Activity Inequality + Gender Gap

This led to the next interesting finding, which showed that 43% of activity inequality was explained by a gender gap; women were significantly less active than men. While there are some countries and cultures where women walk less, obesity rates among women rose in countries with low overall activity and high activity inequality.

3. Activity Inequality + Income Inequality

The researchers then did two different statistical modeling experiments. In one, they tried to model what would happen if they closed the income inequality gap by providing more income to the lower income group. The model predicted that there would be a 400% greater reduction in obesity in targeted therapy and policy, versus population-wide approaches. This has significant potential impact on how and where we choose to use our limited resources.

4. Activity Inequality + A City’s Walkability

The next analysis looked at the “walkability” of a city and if it played a factor in overall activity and activity inequality. Researchers found that the results of a “walkable” city or environment were,

  1. More steps,
  2. Less activity inequality, and
  3. A lower obesity rate.

This has implications on civic planning as a way to impact obesity, health, and health care costs going forward. Walkability increased activity across the board: men and women, the “average weight” population, and even the obese.

Here’s what we can glean from the study:

  1. Walking works. Walking more leads to less obesity.  The National Weight Loss Registry (which I’m a part of) looks at people who have lost a significant amount of weight and have kept it off for at least two years. What they’ve found is that, by far, the most common exercise was plain old walking.
  2. We should focus on closing the gender gap and encouraging women to walk more, and consider what the root cause for women walking less might be. The possible explanations are endless, but some that come to mind are:
    1. Foot pain from uncomfortable, heeled shoes.
    2. Women tend to be in charge of childcare, which often entails sitting and watching the younger children, while fathers go out and play with the older kids. This could add to the gender gap.
    3. Survey data is very clear in that women do not feel safe running alone as a high percentage have been at least verbally accosted if not physically.
  3. It’s not the healthy folk that needs hospitals, just as it’s not the runners that need to hear this message. We need to encourage our less active friends to get a bit more active! We don’t need to guilt them into running a marathon with us, but maybe inviting them to a walk with us after dinner, or take the stairs with us at the mall, or park a few spots further from the building on purpose.

It’s time to step it up!


About the Author

Harvey Hahn, MD, FACC

Dr. Hahn graduated from Loma Linda University in 1994. He is currently the director of the Cardiovascular Fellowship Training Program at the Kettering Medical Center in Kettering Ohio.

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