Obesity is a disease that affects 17% of French people and whose causes and factors can be multiple. It also constitutes a major risk factor for chronic pathologies, such as diabetes or high blood pressure and has significant psychological and social consequences. A major study, published on July 14 in the American scientific journal PNAS, attempts to understand the causes based on a simple observation: obesity is rarer in less developed countries, contrary to what we observe in the West.
For what? In the United States, mainstream thinking and public health messaging have long suggested that populations in developed countries lead relatively sedentary lives, thereby burning fewer calories than people in less industrialized countries. This vision of a lazy, less athletic population would partly explain the greater prevalence of obesity in the West. However, this new study challenges this preconceived idea, as reported in an article in the Washington Post.
Few large-scale studies have rigorously compared energy expenditure between people more likely to develop obesity and those more resistant to it. Herman Pontzer, professor of evolutionary anthropology and global health at Duke University, North Carolina, emphasizes that people with obesity cannot be effectively helped without first understanding its root causes. For this new study, Herman Pontzer and 80 co-authors analyzed data collected by laboratories around the world to precisely measure a person’s energy expenditure, metabolic rate and body fat percentage.
The researchers thus compiled the results of 4,213 men and women from thirty-four countries or cultural groups, covering a wide socio-economic range, from African tribes to Norwegian executives. They were able to calculate each participant’s total daily energy expenditure, as well as their basal metabolism (the number of calories burned for vital functions) and energy expenditure linked to physical activity.
Surprising results
The scientists adjusted the data based on the size of the guinea pigs, because people in developed countries generally have larger builds and therefore expend more calories. The research team compared the different groups and revealed an unexpected finding: those who thought that the differences in energy expenditure were considerable between, for example, hunter-gatherers, pastoralists and office workers were wrong.
According to Herman Pontzer, these results show that“there is no effect of economic development on size-adjusted physical energy expenditure”. In this context, the problem is therefore not a lack of physical activity. Thus, increasing exercise alone would likely have limited impact on reducing obesity.
The authors of the study specify: “Our analyzes suggest that an increase in energy intake was approximately ten times greater than the decrease in total energy expenditure in the modern obesity crisis.” In other words, we consume too much, and often too much, of unhealthy foods. Analysis of the diets of the different groups reveals a strong correlation between a high consumption of ultra-processed foods and a higher body fat rate.
Herman Pontzer nevertheless reminds us that physical activity remains essential for health, even if, to effectively combat obesity, it will be necessary to prioritize the reduction of ultra-processed products in our daily diet.
