A groundbreaking international study has shattered a long-held tenet of public health: that simply eating fewer calories and exercising more is the surest route to weight control. Instead, the research points to ultra-processed foods (UPFs) — industrial formulations containing five or more ingredients — as powerful, independent drivers of the global obesity epidemic, casting doubt on the decades-old mantra of ‘calories in, calories out’ as the full story behind weight gain. The findings, published this week in the Proceedings of the National Academy of Sciences (PNAS) and widely reported in reputable outlets such as the Washington Post, are sparking urgent debates among health experts and raising vital questions for Thailand’s food culture and public health strategy [Washington Post][PNAS article summary].
For years, the dominant advice was simple: to lose weight, eat less and move more. However, researchers have now demonstrated that not all calories are metabolized equally. In a rigorously controlled clinical trial, participants were assigned to diets either rich in ultra-processed foods or emphasizing minimally processed, whole foods. Both diets were calibrated to resemble each other in total calories, fiber, macronutrient ratios, sugar, and sodium. The only major difference: the level of processing. Astonishingly, those on the UPF-heavy diet consistently ate more total calories, felt less full, and gained significantly more weight than their counterparts, even though physical activity levels were held constant and closely monitored.
These findings strike at the core of conventional wisdom and highlight a central role for diet quality — not just quantity — in determining body weight. “It’s not simply that people lack willpower or aren’t exercising enough. These foods disrupt the body’s natural hunger and fullness mechanisms, making it extremely easy to overeat,” noted a global health professor from a research university in North Carolina, who led the new PNAS study. The research resonates with findings from a comprehensive 2024 BMJ meta-analysis that linked UPF consumption to obesity and a range of chronic diseases, though the mechanisms are just beginning to be unraveled [Wikipedia].
Ultra-processed foods, as defined in the Nova classification system, include much of what now populates modern supermarket shelves: instant noodles, packaged snacks, soft drinks, mass-produced breads, frozen meals, and many “diet” or convenience products. These are engineered for maximum palatability, often incorporating rapidly absorbed fats and sugars, artificial colors, flavors, emulsifiers, and other industrial additives. The combination appears to short-circuit the body’s normal satiety signals — the neurohormonal brakes that should tell us when to stop eating [Washington Post].
A pivotal detail of the new research is its global scope. By analyzing data from more than 4,200 individuals across 34 culturally and economically diverse groups — from Tanzanian hunter-gatherers and Bolivian forager-farmers to urban professionals in highly developed nations — researchers debunked the myth that modern lifestyles are simply more sedentary or burn fewer calories. Surprisingly, daily energy expenditure, when adjusted for body size, was remarkably similar across population groups, regardless of industrialization or activity level. The real culprit was dietary: Increased caloric intake, particularly from UPFs, was approximately 10 times more strongly linked to obesity rates than declining physical activity levels.
Expert reactions have been swift. A professor at the Gillings School of Global Public Health commented, “This study confirms what I’ve been saying — diet is the key culprit in our current obesity epidemic.” The director of the Food is Medicine Institute at Tufts University agreed: “Changes to our food, not our activity, are the dominant drivers of obesity. Public health efforts must target ultra-processed foods, which seem to be really potent causes of obesity,” he told the Washington Post.
The implications for Thailand, a country where traditional markets and home-cooked meals still play a prominent role — yet where the market share of convenience and processed snacks continues to surge — could hardly be more relevant [Wikipedia]. According to 2023 data, ultra-processed foods made up 25%-35% of total calorie intake in medium-consumption countries; while Thailand’s exact percentage remains unclear, recent urbanization trends and aggressive marketing by multinational food companies mean Thais are increasingly exposed to the same dietary risk factors as Western populations.
Thailand has witnessed a worrisome rise in obesity, particularly among children and adolescents. The Thai National Health Examination Survey has reported year-on-year increases in overweight and obesity rates, especially in urban areas, mirroring shifts in dietary patterns toward processed snacks, sugary drinks, instant foods, and ready-to-eat meals. Experts in Thai public health nutrition have repeatedly warned that the traditional Thai diet — once rich in vegetables, lean proteins, herbs, and moderate portions of rice — is under threat by the encroachment of processed and fast foods, especially in Bangkok and provincial centers.
Importantly, the new study refutes the idea that increased physical activity alone can compensate for a heavily processed diet. “Exercise is essential for health,” the senior study author emphasized, “But this research shows that if we want to reverse rising obesity, we need to focus far more on reducing ultra-processed food consumption.” This message is especially crucial given the popularity of gym culture and fitness trends in Thai cities, often paired with high-calorie convenience foods. Even consistent exercise, the new evidence shows, cannot fully counteract the metabolic impacts of a UPF-heavy diet — a finding that demands a shift in both personal and policy-level health strategies.
Thailand’s Ministry of Public Health and academic researchers have called for renewed efforts to educate the public on the dangers of excess sugar, salt, and fat found in processed foods. Yet the deeper message of the latest research is that it’s not just about these nutrients themselves — it’s the engineered nature of UPFs that promotes mindless overeating, alters gut hormone responses, and may even change the brain’s reward pathways. As a 2025 review in the journal Metabolic Dysfunction-Associated Steatotic Liver Disease noted, UPFs can prompt changes in the gut microbiome and increase inflammation, potential triggers for metabolic dysfunction and chronic illness [PubMed].
The Nova classification, controversial in nutrition science for its broad definitions, has nevertheless been instrumental in tracking global food trends. Critics argue the system can oversimplify or stigmatize certain foods — pointing out that some processed products, when consumed in moderation and as part of a balanced diet, may play a helpful role, especially for people with time constraints or limited access to fresh ingredients. Others, however, maintain that the unique combination of processing methods and additives in UPFs represents a fundamentally different dietary risk, one not adequately captured by simply counting calories or fat grams [Wikipedia].
Thailand’s rich culture of home cooking, communal eating, and local market tradition offers both a protective buffer and a challenge. While fresh vegetables, herbs, spices, and fresh seafood are still readily available and celebrated in Thai cuisine, the affordability, convenience, and aggressive marketing of UPFs continue to lure families, especially in cities. Popular local snacks — from sweetened beverages to crisped rice bars and instant noodles — may be more processed than recognized. The juxtaposition of these dietary shifts with rising obesity and diabetes rates demands an urgent public health response.
International experience offers valuable lessons. In countries where UPF intake reached over 50% of daily calories (such as the US and the UK), links to obesity, diabetes, and cardiovascular diseases became stark. Public policy in Latin American countries like Chile, where processed food intake rose sharply, has responded with front-of-pack warning labels, advertising restrictions, and educational campaigns — interventions supported by a growing bank of evidence [Wikipedia].
As Thailand debates food labeling, advertising to children, and nutritional education curricula, the latest global research provides clear direction: focus on reducing ultra-processed food consumption, limit aggressive marketing practices, and support the preservation of traditional cooking habits. Grassroots community dining initiatives, urban gardening, and efforts to increase access to fresh, whole foods — including through online platforms and delivery services — can offer scalable, sustainable solutions.
Looking forward, the research community is calling for deeper studies in Asian contexts, given differences in culinary tradition, food environment, and cultural perceptions of weight and health. Policy-makers, educators, and the Thai food industry must consider how to improve public understanding of food processing’s role in health, encourage innovation in minimally processed convenience options, and balance economic interests with the urgent need to curb obesity. Like elsewhere, there must be public dialogue about the unseen risks inside colorful packaging.
For Thai readers: start by checking ingredient lists and opting for foods with fewer additives, lower sugar and sodium content, and those closer to their natural state. Incorporate more fresh produce, whole grains, legumes, and traditional recipes into daily meals. Parents should model balanced eating habits for children, resist the allure of heavily marketed snacks, and favor local markets over convenience stores when possible. Most importantly, recognize that healthy eating is not simply about willpower or exercise; it’s increasingly about navigating a food system engineered for overconsumption. Urge government and community leaders to expand local food access and demand better food labeling and regulation.
As the science evolves, so too must Thai society’s approach to food and health. The latest findings remind us that the path to wellness is not paved solely by self-discipline, but also by the choices that food companies, policy-makers, and communities make together.