If French fries have been your go-to order at restaurants and a favoured side dish with meals, then it might be time to cut them out of your life. According to a new study published in The BMJ on August 6, 2025, the potato-based dish can elevate the risk of Type 2 diabetes by 20%.



But, if you swap these out for whole-grain foods, these odds could decrease by 19%, according to the same study.



The study focused on data involving more than 205,000 people enrolled in the Nurses' Health Study, the Nurses' Health Study II and the Health Professionals Follow-up Study. The participants filled out detailed dietary questionnaires for a long period for three decades, which included questions about how many times a week they ate French fries, whether they baked, boiled or mashed potatoes and how many times they ate whole grains in a week.



Their health was also tracked to gain results, and over the period, a shocking 22,299 participants developed Type 2 diabetes.



“The public health message here is simple and powerful: Small changes in our daily diet can have an important impact on the risk of type 2 diabetes. Limiting potatoes — especially limiting French fries — and choosing healthy, whole grain sources of carbohydrate could help lower the risk of type 2 diabetes across the population,” said Dr Walter Willett, study co-author and professor of epidemiology and nutrition at Harvard University.

Who is to blame: French fries or potatoes?


However, is it the fries or the vegetable itself? “We’re shifting the conversation from, ‘Are potatoes good or bad?’ to a more nuanced — and useful — question: How are they prepared, and what might we eat instead?” said Seyed Mohammad Mousavi, a postdoctoral research fellow in Harvard's Department of Nutrition and lead author of the study.



It does matter how the potatoes are cooked. While just three servings a week of French fries elevated the diabetes risk by 20%, eating the vegetable as baked, boiled or mashed had absolutely no influence on the risk of the disease.



Whole grains for the rescue






Replacing the French fries order with whole grains, such as whole grain pastas or bread, reduced the risk of the disease by up to 19%. Even substituting whole grains with refined ones can add to the lowered diabetes risk.



These findings were substantiated by 2 separate analyses where data from numerous previous studies involving more than 500,000 people led to similar results when it came to the battle of French fries versus whole grains .



“For policymakers, our findings highlight the need to move beyond broad food categories and pay closer attention to how foods are prepared and what they’re replacing," Willett said in a Harvard news release. "Not all carbs — or even all potatoes — are created equal, and that distinction is crucial when it comes to shaping effective dietary guidelines.”