Globally, obesity is increasing faster in rural areas than in cities, a new study suggests.

A network of over 1,000 researchers worldwide analysed global trends in body mass index (BMI), which is a measurement of height and weight.

They looked at BMI data involving over 112 million people living in rural and urban areas in 200 countries and territories between 1985 and 2017.

They found that during that time period, BMI rose by an average of 2.0 kg/m2 in women and 2.2 kg/m2 in men globally. This is equivalent to each person gaining 5-6kg (11-13lbs) in weight.

Over half of this global rise in BMI during these three decades was due to increases in rural areas. In fact, in some low- and middle-income countries, rural areas were responsible for over 80% of this increase.

The researchers found that since 1985, the average BMI in rural areas increased by 2.1 kg/m2 in both women and men. However in cities, the increase was 1.3 kg/m2 in women and 1.6 kg/m2 in men.

The study noted that in 1985, people living in urban areas in over three-quarters of the countries studied had a higher BMI than their rural counterparts. However, by 2017, this gap had shrunk or even reversed.

"The results of this massive global study overturn commonly held perceptions that more people living in cities is the main cause of the global rise in obesity. This means that we need to rethink how we tackle this global health problem," commented the study's senior author, Prof Majid Ezzati, of Imperial College London in the UK.

He pointed out that discussions about public health tend to focus on the negative aspects of city living, when 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," Prof Ezzati added.

Details of these findings are published in the journal, Nature.