The debate between what is more important or the driving factor behind the rising cases of obesity may be solved now. Thanks to the new research led by over 50 institutions across 19 countries that revealed it is diet, or in simpler words, the calorie consumption and not the lack of physical activity that is a dominant factor driving obesity. The study is published in the Proceedings of the National Academy of Sciences (PNAS). The study is more so important because it challenges the belief that sedentary lifestyle is the primary cause of driving the obesity rates high.What Did The Study Find?The study found that higher calorie intake actually plays a much larger role in obesity than reduced physical activity. Despite decades of research into the causes of the obesity crisis, the relative importance of diet versus physical activity has remained uncertain,” said Herman Pontzer, professor of evolutionary anthropology and global health at Duke University, and one of the study’s authors. “The IAEA’s Doubly Labelled Water Database has allowed us to finally test these ideas on a global scale and bring clarity to this major public health challenge.”What Is IAEA? Why Does It Matter?IAEA stands for the International Atomic Energy Agency. The research recently published used IAEA's Doubly Labelled Water (DLW) Database, which is one of the world's largest collections of energy expenditure data. The dataset was able to provide the researchers a look into the balance between energy intake and energy output across the populations and economies. Is Global Obesity On The Rise?In 2022, nearly 1 in 8 people worldwide were living with obesity. This is a number that has doubled more in adults and quadrupled among adolescents in the past three decades. Obesity also increases risk of many chronic illnesses and diseases, including diabetes, cardiovascular disease, and also certain cancers.While industrialized societies see soaring obesity rates, traditional and farming communities experience much lower levels of obesity, a contrast often attributed to more physically demanding lifestyles.This is where this recent study plays a big role. The study found that this assumption does not fully hold true. Even though physical activity across population, or the energy expenditure, that is the total calories burned daily is not significantly lower in industrialized population, their body size is larger. So, if not the energy output, then what is the reason? The answer lies in the diet. How Was The Study Conducted?The researchers analyzed data from 4,213 adults aged 18 to 60, representing 34 populations across six continents. Participants included hunter-gatherers, farmers, and urban dwellers. Using the DLW technique, the researchers measured total energy expenditure (TEE), basal energy expenditure (BEE), and active energy expenditure (AEE).Although people in industrialized nations had higher total energy expenditures due to their larger body sizes, their activity levels, when adjusted for body size, were only slightly lower than those in traditional societies. This slight difference explained less than 10% of the overall increase in body mass index (BMI) and fat percentage. The main driver was higher calorie intake, often from ultra-processed, high-fat, and high-sugar foods.Findings: Diet Matters More“For public health professionals, these findings emphasize that improving diet quality, and reducing consumption of high-calorie, ultra-processed foods, may be far more effective than focusing solely on physical activity,” explained Cornelia Loechl, Head of Nutritional and Health-related Environmental Studies at the IAEA. “It underscores how impactful scientific data can guide better health policies.”Thomas M. Holland, a physician-scientist at RUSH University in Chicago, who was not involved in the study, added: “This research reminds us that while exercise remains essential for overall health, obesity appears to be more closely tied to what and how much we eat. Economic development offers access to more food, but also increases exposure to obesogenic diets.”
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