The age-old debate over whether poor diet or insufficient exercise is the main culprit behind rising obesity rates has taken a new turn, with a major international study concluding that the overconsumption of calories — especially from ultra-processed foods — is far more responsible for obesity than a lack of physical activity. The research, published in the Proceedings of the National Academy of Sciences, analyzed an unprecedentedly diverse cohort and challenges assumptions long held in both public health messaging and everyday Thai life.
For decades, Thais and people worldwide have been urged to “move more” as a primary defense against gaining weight, mirroring campaigns like the Ministry of Public Health’s “30 Minutes for Good Health.” Yet obesity has continued to rise, not only in Western countries but increasingly across Thailand, spurring concerns about non-communicable diseases such as diabetes, hypertension, and heart disease (WHO Southeast Asia). This latest research is significant because it shifts focus from activity levels to dietary choices, particularly the growing intake of ultra-processed foods (UPFs) such as instant noodles, packaged snacks, and sugary drinks now common in Thai convenience stores and homes.
Led by researchers from around the globe, including expert Amanda McGrosky and her team, the study analyzed data from over 4,200 adults aged 18 to 60 across 34 populations spanning six continents. Participants ranged from hunter-gatherers and farmers to urban dwellers in highly industrialized societies, a scale unheard of in previous obesity studies. The methodology was rigorous: the team assessed total energy expenditure (TEE), activity energy expenditure (AEE), and basal energy expenditure (BEE) and compared these to two key obesity markers — body mass index (BMI) and body fat percentage.
At first glance, the data appeared to support a familiar narrative: higher rates of obesity were observed in more economically developed countries, which also showed higher overall energy expenditure. However, when the researchers adjusted for factors such as age, sex, and body size, a surprising trend emerged. Higher levels of activity energy expenditure were present even in developed countries plagued by obesity. In other words, people in richer societies were, on average, more active than assumed — yet still gaining weight. The implication: exercise alone is not the main factor in obesity (Medical Xpress).
Instead, the study found that total energy expenditure was only weakly associated with rates of obesity, accounting for just about 10% of the difference in obesity between more and less developed countries. The real driver, the authors argue, is dietary: specifically, a high intake of ultra-processed foods, which now make up a significant portion of daily calories in many industrialized and rapidly developing countries, including Thailand. The correlation between the percentage of UPFs in the diet and body fat percentage was striking, indicating that what people eat — and how much of it is highly processed — is a far more important factor than their average physical activity.
As the team described, ultra-processed foods are characterized by “hyperpalatability, energy density, nutrient composition, and appearance” that disrupt normal hunger cues and satiety, leading people to overeat. Furthermore, the processing itself can increase the proportion of calories that are actually absorbed by the body, compounding the problem. In layman’s terms, not only do these foods tempt people to eat more than they need, but the body is also more efficient at extracting energy from them.
The researchers emphasized that this does NOT mean exercise should be neglected. The team highlighted the “key role” of regular physical activity in preventing disease and maintaining mental well-being. However, they urge governments, health bodies, and individuals to prioritize reducing calories from highly processed food sources if meaningful progress is to be made on the obesity crisis. This is particularly relevant in Thailand, where modern, busy lifestyles have led to a sharp increase in consumption of packaged snacks, energy drinks, and ready meals — a significant departure from traditional Thai diets rich in vegetables, fresh herbs, and unprocessed grains (Bangkok Post, Matichon).
A leading nutritionist at Mahidol University, commenting on the study, noted, “We have long recognized that Thai children, as well as adults, are eating more ultra-processed foods each year. This study confirms the urgent need to reduce UPF’s role in our diets if we hope to halt rising obesity and related chronic diseases.” A senior official at the Bangkok Metropolitan Administration Public Health Department echoed this sentiment, stating that while exercise is important, “it is no substitute for a balanced diet focused on whole foods, fresh produce, and traditional Thai staples.”
Another key point in the research is the unique nature of UPFs and their connection to the global rise in obesity. Unlike foods traditionally eaten in Thailand — such as som tam, steamed fish, or fresh fruit — UPFs undergo industrial processes such as extrusion, molding, and refining, and often contain additives for flavor, color, and shelf life. These features make them not only highly caloric but also easy to overconsume. Studies cited by the authors have shown that populations rapidly adopting Westernized diets rich in UPFs exhibit spikes in obesity within a generation (The Lancet).
This phenomenon is visible in many Thai communities. A survey by the Ministry of Public Health found that nearly half of Bangkok teenagers regularly consume packaged snacks and sugary drinks, a marked departure from only a decade ago. Additionally, household expenditure data indicates a rise in spending on ready-to-eat foods, which often have low nutritional quality and high caloric density (NSO Thailand).
Historically, Thai cuisine has emphasized balance, freshness, and variety, with meals built around rice, abundant vegetables, lean proteins, and aromatic herbs. However, Thailand’s rapid urbanization and economic growth have paralleled a shift toward convenience foods — part of a pattern seen across Asia. This dietary transition, researchers warn, has made it easier than ever before to eat too many empty calories.
Looking ahead, this research could have profound implications for Thailand’s public health strategy. Current campaigns focus intensely on promoting physical activity, often in schools and workplaces. While these should continue, the authors of the PNAS study recommend a pivot: stronger regulation of the food industry, clearer labeling on UPFs, and education campaigns encouraging consumption of minimally processed foods. Thailand could take inspiration from countries such as Chile, which has imposed strict labeling laws and marketing restrictions on high-sugar, high-fat processed foods with measurable impact on child obesity rates (BMJ).
Importantly, policymakers should also address the economic factors driving UPF consumption. Lower-income families in Thailand often rely on cheap, calorie-dense processed snacks due to constraints on time and money. Subsidizing fruits, vegetables, and other whole foods, as well as providing healthier options in school canteens, could help reverse these trends.
What does this mean for Thai readers seeking to better manage their weight and health? First, it is essential to look beyond exercise as the sole strategy for preventing obesity. Traditional advice to “eat less, move more” is only half the story; reducing intake of ultra-processed foods is crucial. Practical steps include prioritizing whole foods, cooking more often at home, avoiding packaged snacks and sugary drinks, and choosing traditional dishes — many of which are flavorful, satisfying, and naturally low in calories.
For parents and teachers, instilling lifelong eating habits in children is now more important than ever. Educators at leading Thai schools are already integrating lessons on nutrition, cooking, and label reading into the curriculum, equipping students to make healthier choices in an environment saturated with convenience foods.
In summary, this landmark study sends a clear message: while movement and active lifestyles remain core to good health, the real battle in curbing obesity lies in the kitchen and the supermarket. By embracing the wisdom of Thailand’s culinary heritage and resisting the lure of highly processed items on the shelves, Thai families can protect themselves from the rising tide of diet-related disease (Medical Xpress). As the world continues to urbanize and globalize — and as UPFs become ever more available — conscious, culturally-informed dietary choices will be key to securing a healthy future for all generations.