According to a recent study, obesity is increasing more rapidly in the world's rural areas than in the cities.

As part of the study, a team of researchers analysed the height and weight data of more than 112 million adults across urban and rural areas of 200 countries and territories between 1985 and 2017. Height and weight can be used to calculate BMI, an internationally recognised scale which tells us whether an individual has a healthy weight for their height.

The study, involving a network of more than 1000 researchers across the world, found that from 1985 to 2017, BMI rose by an average of 2.0 kg/m2 in women and 2.2 kg/m2 in men globally, equivalent to each person becoming 5-6 kg heavier. More than half of the global rise over these 33 years was due to increases in BMI in rural areas. In some low- and middle-income countries, rural areas were responsible for over 80 per cent of the increase.

The team found that since 1985, average BMI in rural areas has increased by 2.1 kg/m2 in both women and men. But in cities, the increase was 1.3 kg/m2 and 1.6 kg/m2 in women and men respectively. These trends have led to striking changes in the geography of BMI over the three decades. In 1985, urban men and women in over three quarters of the countries had a higher BMI than their rural counterparts. Over time, the gap between urban and rural BMI in many of these countries shrank or even reversed.

"The results of this massive global study overturn commonly held perceptions that more people living in cities are the main cause of the global rise in obesity. This means that we need to rethink how we tackle this global health problem," Majid Ezzati said. The team found important differences between high-, middle-, and low-income countries. In high-income countries, the study showed that BMI has been generally higher in rural areas since 1985, especially for women.

The findings suggest this is due to the disadvantages experienced by those living outside cities: lower income and education, limited availability and higher price of healthy foods, and fewer sports and leisure facilities. "Discussions around public health tend to focus more on the negative aspects of living in cities. In fact, cities provide a wealth of opportunities for better nutrition, more physical exercise and recreation, and overall improved health.

These things are often harder to find in rural areas," Ezzati explained. Meanwhile, rural areas in low- and middle-income countries have seen shifts towards higher incomes, better infrastructure, more mechanised agriculture and increased car use, all of which bring numerous health benefits, but also lead to lower energy expenditure and to more spending on food, which can be processed and low-quality when sufficient regulations are not in place. All these factors contribute to a faster increase in BMI in rural areas. "As countries increase in wealth, the challenge for rural populations changes from affording enough to eat, to affording good quality food," Ezzati added.