A landmark international study published this week in the Proceedings of the National Academy of Sciences (PNAS) is turning conventional wisdom about obesity on its head, revealing that a sedentary lifestyle in wealthy nations may not be the main culprit behind soaring obesity rates. Instead, the research finds that diets high in ultra-processed foods are the leading driver of the modern obesity epidemic, with important lessons for the Thai population and global public health campaigns alike (Washington Post).
For decades, health authorities have warned that people in rich, industrialized countries like the United States and Europe are too sedentary, burning far fewer calories than populations in less-developed regions where physical labor or foraging is the norm. This narrative has also influenced public health messaging in Thailand and across Asia, where rapid modernization is often blamed for rising obesity rates. However, this new study, involving over 4,200 participants from 34 countries across a wide spectrum of cultures and socioeconomic backgrounds—including forager-farmers in Bolivia, hunter-gatherers in Tanzania, and herder-farmers in Siberia—challenges this assumption with hard data.
Using the gold-standard doubly labeled water technique to precisely measure daily metabolic rates and energy expenditure, the international research team found that people in wealthy nations burn roughly the same number of calories per day as those engaged in strenuous physical labor in rural or tribal communities. After adjusting for body size, these similarities persist, despite the vast differences in daily activities and environments. That means a person working as an office executive in a skyscraper in Oslo is expending a similar amount of energy each day as a Tsimane farmer in the Amazon or a Hadza forager in East Africa.
The study’s lead author, a professor of evolutionary anthropology and global health at Duke University in North Carolina, explained that these findings support a relatively new metabolic theory called the “constrained total energy expenditure” model. According to this framework, human bodies tend to regulate daily total energy use within a narrow band, regardless of activity level. If we consistently burn extra calories—say, by walking long distances or training for a marathon—our bodies “compensate” by reducing energy spent on other biological processes like growth, stress response, or immune function. This means that, contrary to popular belief, exercising more doesn’t necessarily lead to dramatically higher daily calorie burn over the long term (PNAS).
If inactivity isn’t causing obesity, then what is? The answer, the authors say, lies primarily in excessive calorie intake—specifically, in the consumption of ultra-processed foods. A key sub-analysis of contemporary and traditional diets in the new study found a strong correlation between the percentage of ultra-processed foods in daily intake and higher levels of body fat. Ultra-processed foods—defined as industrial formulations containing five or more ingredients, typically including added sugars, fats, starches, and additives—are now a staple of diets in wealthy and urbanizing nations worldwide, including Thailand, especially among the youth and working-age population.
One obesity expert from the University of North Carolina at Chapel Hill, unaffiliated with the study, stated, “This study confirms what I’ve been saying, which is that diet is the key culprit in our current [obesity] epidemic.” The sentiment was echoed by the director of the Food is Medicine Institute at Tufts University, who said, “It’s clear from this important new research and other studies that changes to our food, not our activity, are the dominant drivers of obesity.”
The new research doesn’t dismiss the importance of exercise. On the contrary, the Duke professor emphasized that exercise is still vital for overall health, cardiovascular fitness, and prevention of many diseases. However, the data indicate that universally increasing physical activity without addressing dietary changes is unlikely to have a significant impact on the obesity crisis. In practical terms, public health strategies should give priority to reducing the intake of ultra-processed foods and promoting healthier, minimally processed traditional diets.
For Thailand, the findings are both a warning and an opportunity. Although the Thai cuisine is renowned for its use of fresh herbs, vegetables, and home-cooked meals, the country has seen a marked rise in the consumption of packaged snacks, sugary drinks, and fast food over the past two decades. According to the Ministry of Public Health, national surveys show a steady increase in obesity rates, particularly among children and adolescents, mirroring global trends (Bangkok Post). Economic growth and urbanization have led to more sedentary lifestyles among Thais, but this study’s findings point decisively to diet as the more important factor.
Traditional Thai eating habits—which feature fresh vegetables, moderate portions of rice, lean protein, and fermented foods—offer a protective effect against obesity. However, aggressive marketing and easy availability of ultra-processed products are eroding time-honored food customs, especially in urban centers like Bangkok, Chiang Mai, and Pattaya. Stalls selling sweetened drinks and fried snacks proliferate at schools and markets, while convenience foods and instant noodles are now a daily staple in many lower- and middle-class households.
Obesity is not just a matter of physical appearance in Thailand. It is closely linked with a rise in non-communicable diseases (NCDs) such as diabetes, high blood pressure, and heart disease, which are now the leading causes of death nationally. The economic and social costs of these conditions are a major concern for healthcare planners. Therefore, the implications of this latest research extend beyond individual choices—they highlight the need for a systemic, nationwide approach to improving dietary patterns, both through health education and tighter regulation of food marketing.
Experts interviewed in Thai media have pointed out that parents, teachers, and health professionals need to work together to teach young people about the dangers of frequent snacking and excessive consumption of sugary, processed foods. At the same time, government agencies can use taxation and labeling regulations to discourage the purchase of high-calorie, nutrient-poor items. For example, the recent introduction of a sugar tax in Thailand has been a step in the right direction, though its impact has yet to be fully measured (WHO Thailand).
Looking ahead, public health researchers predict that unless dietary patterns shift away from processed convenience foods, obesity and its associated diseases will continue to rise, threatening economic productivity as well as individual well-being. Conversely, there is optimism: Thai culinary culture remains deeply rooted in fresh, home-cooked meals with strong community and family involvement in food preparation and eating. These cultural traditions, combined with evidence-based policies, provide a strong foundation for national efforts to reverse the obesity trend.
For readers looking to take action, health experts recommend focusing on small, sustainable changes. These include reading ingredient labels, preparing meals at home with fresh market produce, reducing portion sizes for rice and high-calorie side dishes, and avoiding regular consumption of packaged snacks and sweetened beverages. Community projects, such as school vegetable gardens or neighborhood cooking contests, can help revive traditional foodways and reinforce healthy habits among children and adults alike.
In conclusion, the latest science makes one thing clear: while physical activity remains crucial for overall health, tackling the obesity epidemic—both in Thailand and around the world—will require a dramatic shift toward whole, minimally processed foods and away from the convenience of ultra-processed products. By leveraging the strengths of Thai food culture and combining them with sound policy and education, the nation can protect future generations from the rising tide of obesity and chronic disease. For more details, readers can consult the original Washington Post coverage (Washington Post article) and the underlying scientific study (PNAS).