A new wave of evidence is reframing a familiar dinner-table debate: potatoes themselves can fit into a healthy diet, but french fries are a different story. A large, decades-long analysis published in The BMJ found that eating french fries about three times a week was associated with a roughly 20% higher risk of developing type 2 diabetes, while baked, boiled or mashed potatoes were not linked to increased risk. The findings, led by researchers at the Harvard T.H. Chan School of Public Health, sharpen guidance for Thai families by focusing on cooking methods rather than demonising a staple ingredient. The practical message: how you prepare potatoes—and what you eat instead—may matter more than the potato itself (BMJ; Harvard Chan School press release).
For Thailand, where diabetes affects nearly one in ten adults and rates of overweight and obesity continue to rise, clear and actionable advice on starchy foods is badly needed. National nutrition guidance already emphasises eating a variety of foods while limiting oil, sugar and salt; this new evidence slots neatly into that framework by distinguishing between minimally processed, home-cooked potatoes and deep-fried fast-food fries, which are often calorie-dense, salty and served in large portions (Global Nutrition Report—Thailand profile; FAO/Thailand dietary guidelines overview).
The BMJ study pooled three famous U.S. cohorts—the Nurses’ Health Study, Nurses’ Health Study II and the Health Professionals Follow-up Study—tracking 205,107 adults over three decades. Participants repeatedly reported how often they ate different forms of potatoes: french fries; baked, boiled or mashed; and chips. After adjusting for an extensive list of lifestyle and dietary factors, researchers found that each increment of three weekly servings of french fries was linked to about a 20% higher hazard of type 2 diabetes, while non-fried potatoes were not significantly associated with higher risk. Total potatoes, across all forms, showed only a modest association with risk, suggesting that fries are the main driver. In complementary “substitution” analyses, replacing baked/boiled/mashed potatoes with whole grains was associated with an estimated 4% lower diabetes risk; replacing french fries with whole grains was associated with a 19% lower risk. Even trading fries for refined grains appeared to reduce risk, underlining just how strongly fries stood out in the data (BMJ; Harvard Chan School press release).
Why does this matter to Thai readers? Thailand’s diabetes burden is substantial and growing, with the most recent global compilation estimating adult diabetes prevalence at 9.7% for both women and men. At the same time, Thai food environments have shifted: more meals are consumed away from home, and fast-food options are ubiquitous, particularly in urban centres and tourist hubs. Surveys during the pandemic years suggested Thai teens were eating fast food at least weekly, alongside a surge in food delivery use—patterns that can normalise large portions of calorie-dense items such as fries. While detailed national statistics on french fry consumption are scarce, per-capita potato intake in Thailand remains relatively low by global standards—around 5–6 kg per person annually—but much of the local consumption is in processed forms linked to fast-food dining and quick-service chains that serve fries by default with burgers, fried chicken and sugary beverages (Global Nutrition Report—Thailand; The Nation coverage of teen fast food habits; PotatoPro Thailand market snapshot, FAO-based).
The Washington Post’s coverage underscores a key nuance: potatoes themselves carry fibre, vitamin C, potassium and vitamin B6—nutrients worth preserving when eaten sensibly, especially if you keep the skin on. As a Boston-based nutrition professor told the Post, “They had some bad press, but now we know it’s really just the french fry.” Experts quoted in the piece point out that fries are often ultra-processed “potato products,” not simply sliced fresh potatoes, with added flours, oils and additives. Deep-frying at high temperatures in large volumes of oil adds calories and salt and can generate harmful compounds—factors that likely contribute to the observed diabetes risk signal. Meanwhile, baked, boiled or mashed potatoes—ideally with the skin left on and minimal added butter or cream—can be part of a balanced plate (Washington Post).
To appreciate the strength of the new evidence, it helps to look under the hood. The BMJ analysis didn’t rely on a single snapshot of diet; it used repeated dietary assessments over decades and carefully adjusted for confounders (including BMI, smoking, activity and other dietary patterns). Results held across several sensitivity analyses. The authors also examined “what if” scenarios, estimating the risk change associated with swapping potatoes for other carbs. Replacing any potato form with whole grains (for example, whole-grain bread or pasta) looked beneficial in the model, with the largest estimated gains from replacing fries. Importantly, the study also synthesised international cohort data in a meta-analysis, reporting a consistent risk elevation for fried potatoes and little to no signal for non-fried forms—an approach that bolsters confidence in the pattern and helps explain why earlier studies, which lumped all potatoes together, delivered mixed results (BMJ).
A few caveats are crucial. This was observational research, not a randomised trial, so it can’t prove causation. The cohorts were predominantly of European ancestry and drawn from U.S. health professionals, which may limit generalisability, though a parallel meta-analysis spanning studies from several continents arrived at similar conclusions for fried versus non-fried potatoes. The reliance on food-frequency questionnaires can introduce measurement error, but the repeated assessments reduce that risk. And while the french fry signal was consistent, the relationship for chips varied across different statistical approaches. Still, across multiple models, fries remained the outlier linked with higher diabetes risk—a consistency that gives public health relevance even if the exact effect size may vary by population or food environment (BMJ).
Experts say the mechanism is plausible. Potatoes are high in rapidly absorbed starch, which can spike blood sugar, particularly in large servings or when paired with sugary drinks and refined carbs. Deep-frying adds fats and salt and can create advanced glycation end-products and other heat-related compounds linked to metabolic harm. Historical shifts in frying oils matter too. In the U.S., fries were once cooked in beef tallow, then moved to partially hydrogenated oils (trans fats) in the 1990s before trans fats were effectively banned in 2018. Thailand adopted a similar protective stance: the Ministry of Public Health banned partially hydrogenated oils in foods in 2019, removing a major source of industrial trans fats from the Thai diet. That policy likely reduced cardiovascular risks, but deep-fried foods remain energy-dense, salty and easy to overeat—properties that can still push metabolic risk upward even without trans fats (BMJ; Resolve to Save Lives—Thailand trans fat elimination case study).
What do Thai health professionals and families do with this information? For one, stop treating “potatoes” as a monolith. Thailand’s food-based dietary guidelines already encourage variety and moderation and advise limiting oil, sugar and salt—the very elements that make french fries nutritionally risky. In practical terms, that means favouring home-cooked, non-fried potatoes in reasonable portions and reserving fries for occasional treats if at all. The American Diabetes Association’s plate method, widely used by clinicians, offers a simple visual: half the plate non-starchy vegetables, a quarter lean protein, and a quarter carbohydrate foods (such as rice, whole grains—or a modest serving of starchy vegetables like potatoes). That balance can be applied directly to Thai meals—pairing a small serving of khao suay or brown rice with a lean protein and a generous variety of non-starchy vegetables, and keeping starchy sides like potatoes in the “quarter plate” lane (FAO/Thailand dietary guidelines overview; American Diabetes Association—Eating Healthy).
Culturally, there is room to adapt without sacrificing flavour. Thai households that enjoy gaeng massaman—one of the few traditional dishes where potatoes feature prominently—can keep the potato pieces but consider lighter versions: smaller portions of potato per person, more non-starchy vegetables in the pot, leaner cuts of protein, and a restrained hand with coconut cream. For crispy textures, air-frying or oven-roasting seasoned potato wedges (skin-on) uses much less oil than deep-frying; served alongside a salad, nam phrik with raw vegetables, or stir-fried morning glory, this can satisfy cravings without the salt-and-fat overload that often accompanies takeaway fries. Nutrition experts interviewed by the Washington Post also suggested cooling boiled potatoes before eating to boost resistant starch—a type of carbohydrate that digests more slowly and may improve glycaemic control—though this is a small tweak, not a magic bullet (Washington Post).
The study also reinforces the power of smart swaps. In Thai contexts, “whole grains” need not mean imported bread or pasta. Substituting brown rice, riceberry, mixed-grain rice, or whole-grain noodles for a portion of starchy sides can nudge glycaemic responses and satiety in the right direction. Legume-rich dishes—from mung bean desserts with less sugar to tofu stir-fries—also fit the substitution logic. The Harvard team’s modelling suggested even refined grains were a better bet than french fries in terms of diabetes risk, though whole grains remain preferable where available and affordable (Harvard Chan School press release).
Outside the home, portions and pairings add up. Ordering a small side rather than large fries, skipping sugary sodas, and doubling down on non-starchy vegetable sides can collectively blunt risk. Quick-service restaurants in Thailand have grown more diverse, and menus increasingly include salads, grilled proteins, and rice bowls with vegetable sides. The country’s ban on partially hydrogenated oils has improved the baseline healthfulness of frying fats, but smart consumer choices—less deep-fried food, fewer oversized portions—still matter most in preventing diabetes and cardiovascular disease (USDA FAS—Thailand HRI foodservice overview; Resolve to Save Lives—Thailand trans fat elimination).
This is not a licence to binge on chips. While the BMJ study’s main analyses did not find a significant association between chips (including potato and corn chips) and diabetes risk, results for chips varied across methods, and chips carry their own nutritional downsides: high sodium, low fibre and easy overconsumption. The absence of a strong signal here should be read as “focus first on the big, consistent problem (fries),” not as “chips are metabolically harmless.” In a Thai snacking culture that increasingly includes savoury packaged snacks alongside traditional choices, sensible portions and label literacy remain essential (BMJ).
Comparisons to earlier research show why this new analysis is influential. Prior studies reached conflicting conclusions because they often combined all potato types, obscuring the unique risk profile of fries. By disaggregating potatoes by cooking method, tracking diets over decades, and modelling real-world food substitutions, the Harvard team offered a more practical lens for both households and policymakers. As the corresponding author noted in the press release, nutrition policy needs to move beyond broad categories and ask how foods are prepared and what they replace—advice that resonates with Thailand’s own efforts to shape healthier food environments in schools, hospitals and public institutions (Harvard Chan School press release).
There are also economic and access dimensions. Potatoes are inexpensive and filling, which matters for households balancing budgets, especially as food prices fluctuate. The Washington Post notes that a small potato with the skin offers fibre and key micronutrients at low cost. Public health strategies in Thailand can adopt a “healthier preparation first” message: encourage markets, school canteens and community kitchens to promote boiled, steamed or roasted potatoes in modest portions, paired with plenty of non-starchy vegetables and legumes. Given that per-capita potato intake in Thailand is relatively low, the bigger win may be reducing the frequency and portion size of fries in the out-of-home food sector and promoting whole-grain swaps where feasible (Washington Post; PotatoPro Thailand—consumption overview).
As always, context is king. Thailand’s diabetes landscape is shaped by far more than potatoes: sugary beverages, high-sodium and high-fat prepared foods, sedentary time, and sleep patterns all play roles. But the fries finding is actionable because it pinpoints a popular, modifiable behaviour with a clear alternative: choose non-fried preparations or swap toward whole grains. The evidence fits neatly with the Thai “nutrition flag” guidance to limit oils, sugar and salt while keeping starchy foods in proportion with other food groups. Clinicians can use this study to update counselling scripts: if a patient loves potatoes, recommend skin-on, boiled or roasted forms in small portions, and suggest swapping fries for a side of vegetables or brown rice. For those with prediabetes or multiple risk factors, suggest temporarily eliminating fries to assess impact on weight and glucose control, while emphasising sustainable, enjoyable eating patterns (FAO/Thailand dietary guidelines overview; American Diabetes Association—Eating Healthy).
Looking ahead, researchers will likely probe how different oils, frying temperatures, potato varieties and restaurant practices influence risk. The BMJ paper noted that BMI mediated about half of the association between fries and diabetes, implying that weight gain from calorie-dense fried foods is a major pathway. But the persistence of risk even after accounting for BMI hints at additional mechanisms—from glycaemic load to heat-generated compounds. For Thailand, this suggests a dual strategy: population-level measures that lower exposure to calorie-dense fried sides (for example, defaulting to non-fried sides in institutional meals) and individual counselling that normalises smaller portions and smarter swaps. Monitoring trends is also important. The quick-service sector is dynamic, and product reformulation (less salt, better oils) may shift risk profiles over time—much as the trans fat ban did. But none of these changes negate the core behavioural takeaway: fries are best kept rare (BMJ; Resolve to Save Lives—Thailand trans fat elimination).
For Thai households ready to act today, the playbook is straightforward. At home, boil, steam or roast potatoes with the skin on; season with herbs, lime and a pinch of salt instead of heavy sauces; cool and reheat for more resistant starch if you enjoy the texture; and keep portions modest—roughly a fist-sized serving on a quarter of the plate. If you crave crunch, use an air fryer with minimal oil. When eating out, swap fries for vegetables, soup or a small portion of rice, and choose water or unsweetened drinks instead of sodas. For school and workplace canteens, set defaults to non-fried sides and whole grains, making fries an opt-in, small-size extra. These small decisions, replicated across millions of meals, can help bend Thailand’s diabetes curve in the right direction—one side dish at a time (Washington Post; American Diabetes Association—Eating Healthy).
Thailand has shown it can act decisively on nutrition policy, as the 2019 elimination of industrial trans fats demonstrated. Building on that momentum, policymakers and industry can nudge the food environment further: highlight non-fried sides on menus, price smaller fry portions more attractively than large sizes, and promote whole-grain options in combo meals. Public campaigns can refresh the nutrition flag message for modern eating patterns, emphasising that how we cook matters as much as what we cook. And researchers can continue to track dietary patterns, particularly among youth, as food delivery and convenience trends reshape daily eating. With rigorous evidence now pointing squarely at fries as the outlier among potato preparations for diabetes risk, Thailand has a clear, culturally adaptable target for prevention efforts (Resolve to Save Lives—Thailand trans fat elimination; The Nation—teen fast food habits).
Bottom line for Thai readers: don’t fear the potato, but respect the fryer. The best available evidence says non-fried potatoes can fit into a healthy Thai diet when eaten in sensible portions, but french fries should be an occasional indulgence, not a weekly habit. If you want to lower your diabetes risk, start with small, sustainable swaps—trade fries for whole grains or vegetables, keep the potato skin on, and make non-fried cooking your default. Your glucose levels—and your long-term health—will thank you.
Sources: The BMJ study on potato intake and type 2 diabetes risk (BMJ); Harvard T.H. Chan School news release summarising the findings and substitutions (Harvard Chan School); contextual reporting and expert commentary on preparation methods and nutrition (Washington Post); Thailand’s dietary guidelines emphasis on limiting oil, sugar and salt (FAO/Thailand); national NCD context (Global Nutrition Report—Thailand); Thailand’s elimination of industrial trans fats (Resolve to Save Lives); Thai fast-food consumption signals among youth (The Nation); and sector background for eating out trends (USDA FAS—HRI report).