Translation. Region: Russian Federal
Source: United Nations – United Nations –
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September 13, 2025 Healthcare
New nutrition research from the International Atomic Energy Agency (IAEA) suggests that the main cause of obesity in rich countries is increased calorie consumption, not decreased physical activity as previously thought.
The findings, published as an article in the journal Proceedings of the National Academy of Sciences, challenge the idea that decreased physical activity is driving the rise in obesity associated with economic development.
“Despite decades of efforts to understand the underlying causes of the obesity crisis in developed countries, the relationship between diet and physical activity has remained unclear,” said Herman Pontzer, professor of evolutionary anthropology and global health at Duke University and one of the authors of the paper. “The IAEA database has brought together a global effort not only to test new ideas but also to address the uncertainty surrounding this pressing public health issue.”
Global problem
In 2022, almost one in eight people on Earth was obese. Over the past three decades, the rate among adults has more than doubled and among adolescents, it has quadrupled.
A complex chronic condition characterized by excess body fat, it increases the risk of non-communicable diseases such as diabetes, cardiovascular disease and cancer. However, obesity is rare in traditional and agricultural communities, which has been associated with greater physical activity in these areas.
Obesity is caused by an imbalance between the calories you eat and the energy your body burns. Public health experts often point to two causes: overeating and insufficient physical activity. However, the exact role of each is debated, as lower levels of activity do not always mean lower energy expenditure throughout the day.
The lack of diverse and reliable data on calorie intake, energy expenditure, and body composition further complicated the study. Previous attempts to address this issue focused on non-industrialized populations, did not include measures of body fat, and relied on limited information from general consumption data and country-level surveys.
To fill this gap, 68 researchers turned to the IAEA’s Doubly Labelled Water Database, a global bank of energy expenditure measurements collected using stable isotope techniques. The database, which contains information on 45 countries, has previously been used by scientists to conduct groundbreaking research on energy metabolism in the body and to inform current revisions of human energy requirements.
Research into factors influencing obesity
The researchers analyzed the physical condition of 4,213 adults aged 18 to 60 years on six continents, representing 34 population groups with different economic conditions and lifestyles. The scientists noted an increased energy expenditure (both activity-related and overall) among the population of industrialized countries. The main factor contributing to obesity was calorie intake, which the researchers estimated based on measurements of total energy expenditure and weight change.
“For public health and nutritionists, these findings provide new insights into the importance of diet,” said Cornelia Lechl, Head of Nutrition and Health Research at the IAEA’s Division of Health and one of the authors of the paper. “Policies aimed at improving diet quality and reducing consumption of energy-dense, ultra-processed foods are likely to be more effective in combating obesity than promoting physical activity. More broadly, these findings represent a major scientific breakthrough made possible by the IAEA’s human health databases.”
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