However, the researchers found it’s not a country’s average number of steps that is the biggest factor shaping obesity levels. Instead it appears to be “activity inequality”.

In short, if there is a large divide between the fittest and the laziest, a country is more likely to have high obesity levels.

For example, in Sweden, where there was little difference in the number of steps taken by the most and least active people, obesity rates are very low.

Meanwhile, the US and Mexico both have similar average step counts, but in the US, which has higher obesity levels, there was a far greater divide between those who exercised and those who didn’t.

In the five countries with the highest levels of activity inequality, individuals are 196% more likely to be obese than in the five countries where inequality is lowest.

The gender divide

Much of this activity inequality is driven by uneven levels of exercise taken by men and women in different countries. In Japan, men and women exercised to roughly the same degree; the country has low levels of both inequality and obesity.

Compare this with Saudi Arabia, where much of the activity inequality results from the low levels of exercise done by women compared to men.

The study is the latest to capitalize on the vast quantities of data available through smartphones, and is far more extensive than previous research in this area. Researchers hope that insights from this data will help us to find new ways of tackling the obesity crisis.

For example, the team also analyzed how easy 69 US cities were to navigate on foot, and unsurprisingly found a strong correlation between activity levels and ease of walking. They suggest this data could be used to support the development of cities that promote physical activity.