Golden, crispy, and far too easy to love, French fries have earned their place as a universal guilty pleasure. But while they might make our taste buds happy, new research suggests they could be quietly adding to our health troubles.

A large study published in The BMJ on 6 August 2025 has found that eating French fries regularly can raise the risk of developing type 2 diabetes by 20 percent. On the other hand, making a simple swap to whole grains could bring that risk down by nearly the same amount, up to 19 percent.

What the research says

The findings come from an analysis of data from more than 205,000 people who took part in the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-up Study.

For nearly three decades, participants filled in detailed food questionnaires, noting how often they ate French fries, their intake of whole grains, and whether they preferred their potatoes baked, boiled, or mashed.

Over this time, their health was closely tracked and 22,299 participants were diagnosed with type 2 diabetes.

Small changes can have a big impact

“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.

Potatoes or French Fries, which is the real problem?

The research team also looked at whether the risk came from potatoes in general or French fries in particular. As Seyed Mohammad Mousavi, the study’s lead author and a postdoctoral research fellow in Harvard’s Department of Nutrition, explained: “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?’”

Why preparation matters

It turns out that cooking method makes all the difference. Just three servings of French fries a week were linked to a 20 percent rise in diabetes risk. In contrast, baked, boiled, or mashed potatoes were not linked to the disease.

Replacing French fries with whole grains like whole-grain pasta or bread could lower the risk by up to 19 percent. Even switching to refined grains instead of French fries brought some benefit in reducing diabetes risk.

These patterns were confirmed in two other analyses involving more than half a million people, both showing the same results, French fries increased the risk, while whole grains helped reduce it.

Not all carbs are equal

“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 added 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.”