The number of obese people has been growing year by year in most countries of the world. At the same time, the global percentage of urban population has also steadily increased. For a long time, life in big cities has been intuitively associated with higher body mass. However, this belief turns out to be false. The latest international research involving teams of Prof. Grażyna Jasieńska and Prof. Andrzej Pająk from the Institute of Public Health of the Jagiellonian University Medical College has revealed the truth about one of the most dangerous diseases of affluence in today’s world.
During the last 35 years, the number of city dwellers has increased by 14%. At the same time the global average body mass index (BMI) has grown by 2.1 among women and 2.2 among men. As the normal BMI value is considered to be between 18.5 and 24.99, the rise by nearly 10% in both these groups has alarmed public health experts. What’s most interesting is the comparison between the BMI increase in rural and urban population, since it turns out that the former was at least twice as great as the latter. What has caused such a major disparity and what are its broader implications?
Junk food instead of organic produce
During the last century the BMI of country dwellers was always lower than that of people living in cities. Harder physical labour, more household chores and necessity to travel longer distances on foot meant greater energy expenditure among rural population. Additionally, the lower average income in the countryside used to be reflected in the lower calorie intake in their daily diet.
The technological progress increased the mechanisation of agriculture, which went hand in hand with the development of modern infrastructure. As a result, living in the countryside required less physical effort than before, as, for instance, it was no longer necessary to carry water from the well, heating the homestead became easier, less farm work needed to be done manually, and walking became limited due to the availability of motor vehicles. Besides, the economic growth, reflected in the higher income, enabled inhabitants of rural areas to buy more food in grocery stores and, consequently, consume more calories, especially in the form of processed carbohydrates, whose availability also increased. All these factors, collectively referred to as the “urbanisation of rural life”, contributed to a dynamic increase of the rural population BMI.
Obviously, the progress that made living in the countryside easier also occurred in urban areas. Yet, the transition was much more radical for the rural population than for the city dwellers, who had already been more accustomed to change. Besides, the infrastructure of large agglomerations used to provide better access to stored food, which largely eliminated the problem of seasonal shortages - historical data confirms that the scale of urban malnutrition was lower than that of rural population.
It turns out that the problem of rural malnutrition has changed but not disappeared. Historically, it resulted from consuming insufficient amounts of food (undernutrition), whereas today, it’s caused by consuming enough or even too much food, which, however, doesn’t provide the body with enough nutrients.
It should be also noted that the greatest increase in BMI during the last three decades happened in rural populations of low- and medium-income countries. This suggests that easy access to low-quality calories has been a major factor contributing to the changes in eating habits.
No time to waste
The previous hypotheses, associating the rise in obesity with migration from rural to urban areas, made the experts focus on solving this problem in cities. The results of the recent study suggest that the roots of the problem lie elsewhere and public health policymakers should shift the emphasis to dietary patterns of rural population. The health of millions of people is at stake.
Source: NCD Risk Factor Collaboration (NCD-RisC), Rising rural body-mass index is the main driver of the global obesity epidemic in adults. Nature, 569, 260–264, 2019.
Original text: www.nauka.uj.edu.pl