Lack of exercise isn’t the main cause of obesity, new study finds
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Obesity is widely known to be a key driver of health complications and chronic diseases, but the debate over whether poor diet or lack of physical activity plays a greater role continues.
While the body must burn calories through basic functions like breathing and digestion or physical movement, researchers have questioned whether obesity is primarily driven by consuming too many calories or by failing to burn enough through activity.
A new study published in the Proceedings of the National Academy of Sciences (PNAS) suggests that diet — not lack of exercise — is the primary cause.
Researchers from Duke University in the United States analyzed data from 4,213 adults aged 18 to 60 across 34 populations spanning six continents. The sample included people from hunter-gatherer communities, pastoral societies, agricultural regions and modern industrial societies, each with different diets and activity levels.
The study examined total energy expenditure (TEE), activity energy expenditure (AEE), basal energy expenditure (BEE), body fat percentage and body mass index (BMI). AEE refers to the calories burned through physical activity and is calculated by subtracting BEE from TEE. To account for variations in lifestyle and diet across economic development levels, researchers categorized groups using the United Nations Human Development Index (HDI).
Interestingly, TEE, AEE and BEE — as well as BMI and body fat percentage —were all found to be higher in economically developed countries, where obesity rates also tend to be elevated. In other words, people in wealthier countries not only burn more calories overall but also tend to weigh more.
Even after adjusting for factors such as age, sex and body type, the researchers found that AEE was generally higher in more economically developed groups. This led them to conclude that lack of exercise is unlikely to be the main driver of increased BMI or body fat.
While total energy expenditure showed only a weak link to obesity, it explained around 10 percent of the rise in obesity rates in developed nations.
Instead, the researchers point to the overconsumption of ultra-processed foods — including processed meats, instant meals, and snack cakes — as the main cause. The proportion of ultra-processed foods in the diet was positively associated with body fat percentage, the researchers said.
Amanda McGrosky, one of the study’s authors, emphasized that while lack of exercise may not be the main culprit, regular physical activity remains essential as exercise still plays a critical role in disease prevention and mental health maintenance.
This article from Kormedi.com, Korea’s top healthcare and medical portal, is translated by a generative AI system and edited by The Korea Times.