A new international study suggests that excessive calorie consumption—especially from ultra-processed foods—is a far greater contributor to obesity than lack of physical activity.
The research, led by Amanda McGrosky of Duke University, examined data from over 4,200 adults across 34 populations spanning six continents. These populations included a wide variety of lifestyles, such as hunter-gatherers, pastoralists, farmers, and residents of industrialised societies. The study aimed to determine whether obesity is more strongly driven by too many calories being consumed or by too little energy being expended through exercise.
Researchers analysed three key metrics:
- Total Energy Expenditure (TEE) – the total calories burned per day
- Activity Energy Expenditure (AEE) – calories burned through movement and exercise
- Basal Energy Expenditure (BEE) – calories burned by the body at rest, including during digestion and basic functions
Two main obesity indicators—body fat percentage and Body Mass Index (BMI)—were also evaluated.
Interestingly, findings showed that more economically developed nations, where obesity rates are higher, also had higher overall energy expenditure. Even after adjusting for age, sex, and body size, people in these wealthier countries were still burning more calories through activity than those in less developed regions.
This evidence suggests that lack of exercise is not the primary cause of obesity. Instead, what stood out was the greater calorie intake in economically advanced populations, particularly from ultra-processed foods (UPFs).
The study found that the percentage of UPFs in the diet was directly linked to higher body fat levels. Researchers believe that the hyper-palatability, high energy density, altered nutrient composition, and artificial appearance of these foods disrupt natural satiety signals, leading to overeating. Moreover, processing methods increase the absorption rate of calories, meaning more energy is retained in the body instead of being excreted.
Despite these findings, the authors highlighted the critical health benefits of exercise, noting its positive impact on mental health and disease prevention.
In conclusion, the study underscores that while exercise remains important, dietary habits—especially the overconsumption of ultra-processed foods—are the main drivers of obesity in developed societies.