Researchers find French fries preparation, not potatoes, drives diabetes risk
Who doesn’t crave a side of fries with every meal? Unfortunately, eating just three servings a week is linked to a 20 percent higher risk of developing type 2 diabetes, according to research published in The BMJ.
The study found that boiled, baked, or mashed potatoes in similar quantities did not carry the same risk, highlighting the impact of food preparation on chronic disease outcomes.
The findings are based on nearly 40 years of dietary data from over 205,000 US health professionals, with 22,299 cases of type 2 diabetes identified during the follow-up period.
Researchers found that for every three weekly servings of total potato, the rate of type 2 diabetes increased by 5 percent. But French fries alone were associated with a four-fold higher increase.
Replacing three weekly servings of French fries with whole grains lowered the risk by 19 percent, while substituting with baked, boiled, or mashed potatoes reduced the rate by 4 percent.
Replacing any form of potato with white rice, however, was linked to an increased risk.
Seyed Mohammad Mousavi, lead author and postdoctoral research fellow at the Harvard T.H. Chan School of Public Health, said that “not all potatoes are created equal,” and even less than one weekly serving of fries “is associated with a higher risk of type 2 diabetes.”
He explained that deep-frying introduces trans or saturated fats, which may contribute to insulin resistance and inflammation—factors that elevate diabetes risk.
According to Healthline, French fries are classified as ultra-processed foods and often made using reheated oils that break down natural fibre, increase glycemic load, and add harmful compounds.
Caroline Roberts, a nutritional therapist interviewed by Healthline, explained that industrial fries also undergo steps such as sugar coating and partial frying, which increase glycemic index and fat content.
The findings add to previous research.
A 2022 meta-analysis of 1.1 million people, cited by Healthline, showed a 12 percent increased risk of type 2 diabetes with moderate consumption of ultra-processed foods, and up to 31 percent with high consumption.
Nichola Ludlam-Raine, a registered dietitian, told Healthline that “while an occasional portion isn’t likely to cause harm, habitual intake matters.”
She recommended limiting fries to no more than once every couple of weeks and building balanced meals with protein, fibre, and healthy fats.
Mousavi added that baking fries at home with olive or avocado oil could offer a healthier option than restaurant-prepared fries.
He also noted that substituting potatoes with low glycemic index carbohydrates such as whole-grain bread or farro could help mitigate diabetes risk.
Although potatoes are naturally rich in fibre, vitamin C, magnesium, and potassium, their health impact depends heavily on preparation and what they are paired with, according to The BMJ report.
Potato skins, often removed in industrial processing, contain fibre that helps regulate blood sugar, said Shannon Galyean, assistant professor of nutritional sciences at Texas Tech University, in NBC News.
The BMJ researchers noted the limitations of their study, including its observational nature and the lack of diversity in its sample population, which consisted largely of individuals of European ancestry.
They also did not account for added toppings such as butter, bacon, or cheese that could influence the overall calorie and fat content of potato dishes.
Health and Human Services Secretary Robert F. Kennedy Jr. has previously called seed oils in fries “poisoning” and pushed for a return to beef tallow.
However, Mousavi responded that “beef tallow is high in saturated fats and other harmful fats. We definitely don’t recommend that.”
In the study, The BMJ researchers concluded that baked, boiled, or mashed potatoes may be part of a healthy and sustainable diet when consumed in place of ultra-processed options, but whole grains should remain the dietary priority.
