With nearly one in eight people worldwide living with obesity in 2022, the condition has surged dramatically over the past three decades, more than doubling among adults and quadrupling among adolescents. This chronic disease, characterized by excessive body fat, significantly heightens the risk of non-communicable diseases such as diabetes, heart disease, and cancer. Despite its prevalence in industrialized societies, obesity remains rare in traditional and farming communities, a discrepancy often attributed to higher levels of physical activity.
At its core, obesity results from an imbalance between calories consumed and the energy the body expends. Public health experts have long debated the roles of overeating and insufficient physical activity in this equation. While lower activity levels are often assumed to lead to lower energy expenditure, the reality is more complex, as daily energy expenditure does not always decrease proportionally with reduced physical activity.
Research Gaps and New Insights
The lack of diverse and reliable data on calorie intake, energy expenditure, and body composition has historically complicated obesity research. Previous studies have often focused on nonindustrial populations, lacked precise body fat measurements, or relied on limited data from national consumption surveys.
To address these gaps, 68 researchers utilized the International Atomic Energy Agency’s (IAEA) Doubly Labelled Water (DLW) Database. This global resource compiles energy expenditure measurements collected through the DLW stable isotope technique, spanning 45 countries. The database has enabled groundbreaking research on human energy metabolism and informed revisions of human energy requirements.
Findings from a Global Perspective
The researchers analyzed data from 4,213 adults aged 18 to 60 across six continents, representing 34 populations with varying economic statuses and lifestyles. They noted higher energy expenditure in more industrialized economies, both in terms of activity-related energy and overall energy use. However, when adjusting for larger body sizes, the decrease in energy expenditure was minimal, insufficient to explain the significant increases in body mass index (BMI) and fat percentage linked to economic development.
Instead, the study identified energy intake as the primary factor driving obesity. Researchers estimated energy intake by measuring total energy expenditure and weight change, concluding that dietary habits, rather than physical activity levels, were the main contributors to obesity.
“For public health professionals and nutrition specialists, these findings offer novel insights on the importance of diet. Policies which focus on improving diet quality and reducing the consumption of high-calorie, ultra-processed foods are likely to be more effective in combating obesity than those centred solely on increased physical activity,” explained Cornelia Loechl, Head of Nutritional and Health-related Environmental Studies in the IAEA Division of Human Health and one of the article’s authors.
Implications for Public Health Policy
The study’s findings have significant implications for public health policies worldwide. By highlighting the crucial role of diet in managing obesity, the research suggests that efforts to combat obesity should prioritize improving dietary quality over merely increasing physical activity. This approach could involve reducing the consumption of high-calorie, ultra-processed foods and promoting healthier eating habits.
Since its publication, the article has garnered significant attention, being viewed over 72,000 times and featured by more than 165 international news outlets. The widespread interest underscores the global relevance of the study’s findings and the potential impact on future health policies.
As the world grapples with the growing obesity epidemic, these insights offer a pathway to more effective interventions. By focusing on dietary improvements, public health initiatives can better address the root causes of obesity and reduce the burden of related diseases.
The move represents a shift in understanding the complex dynamics of obesity, emphasizing the need for comprehensive strategies that integrate dietary changes with other health-promoting behaviors. As researchers continue to explore the intricacies of human metabolism and energy balance, the IAEA’s human health databases will remain a vital resource in the quest for solutions to this global health challenge.
