LIH contributed to a worldwide public health study published in Nature in May 2019. By analysing trends of body-mass index (BMI) evolution, it revealed that BMI is rising faster in rural than in urban areas. This phenomenon is the main driver of the global obesity epidemic.

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 was assessed to calculate BMI. The researchers found that over the last three decades, 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 in mean BMI and more than 80% in some low- and middle-income countries was due to the increase in BMI in rural areas. The average BMI in rural areas has increased by 2.1 kg/m2 in both women and men, whereas in cities the rise 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. According to the authors the lower urban BMI in high-income countries reflects a growing rural economic and social disadvantage, including lower education and income, lower availability and higher price of healthy and fresh foods, less access to, and use of, public transport and walking than in cities.

The study was conducted in the framework of the Non-Communicable Diseases Risk Factor Collaboration (NCD-RisC) coordinated by the WHO Collaborating Centre on NCD Surveillance and Epidemiology at Imperial College London. Dr Ala’a Alkerwi from LIH’s Department of Population Health was one of over 1,000 collaborators of NCD-RisC.

‘Once again our data from the ORISCAV-LUX study conducted in 2007-2008 with more than 1,400 Luxembourg residents aiming to assess cardiovascular health and risk factors in Luxembourg served in this important international study’, stresses Dr Alkerwi. In Luxembourg, BMI was found to be slightly higher in the countryside than in cities over the defined time frame, but the BMI rise over time is more marked in urban compared to rural areas for both women (1 kg/m2 vs. 0.7 kg/m2) and men (1.1 kg/m2 vs. 1.9 kg/m2), opposite to the global trend. 

The research was funded by the Wellcome Trust, the Medical Research Council, the Royal Society and the Academy of Medical Sciences. The ORISCAV-LUX study at LIH was jointly supported by the Ministry of Health and the Ministry of Higher Education and Research.

Publication: Rising rural body-mass index is the main driver of the global obesity epidemic in adults NCD Risk Factor Collaboration (NCD-RisC), Nature 2019

Estimates of mean BMI by country, year, sex and place of residence (urban and rural) are available on the NCD-RisC website: www.ncdrisc.org