The Unexpected Risks of French Fries

French fries may be tempting, but giving in to temptation might be dangerous. New research reinforces previous findings that French fries are associated with undesirable health outcomes, including type 2 diabetes.

French Fries in America:

Potatoes are the most popular vegetable in the US, and French fries are by far the favorite form of potatoes. According to a recent study, that spells trouble for our metabolic health (BMJ, Aug. 6, 2025). The investigators analyzed detailed dietary and health data every few years from more than 200,000 participants in the Nurses’ Health Study, the Nurses’ Health Study II and the Health Professionals Follow-Up Study. Over the course of three decades, investigators racked up over 5 million person-years of observation. During that time, more than 10 percent of the volunteers developed type 2 diabetes.

The analysis showed that people who ate French fries at least three times a week were 20 percent more likely to get a diabetes diagnosis. The more often participants ate French fries, the higher their chance of that disease. Total potato intake was also associated with type 2 diabetes, but French fries were primarily responsible. People who ate their potatoes mashed, boiled or baked did not run the same risk, for the most part. Body mass index (BMI), a measure of fatness, accounted for about 50 percent of the risk from French fries.

Substituting whole grains such as farro or bulgur wheat for some servings of not-fried potatoes would reduce the risk of diabetes modestly. Swapping whole grains in for French fries, on the other hand, reduced the risk of type 2 diabetes by 19 percent. Eating white rice instead of baked potato would increase the chance that a person might develop diabetes.

According to corresponding author Dr. Walter Willett,

“Small changes in our daily diet can have an important impact on 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.”

We asked Dr. Willett if scientists know why French fries are particularly dangerous for our health. He suggested that trans fats might be part of the picture. Most fast food purveyors are no longer using trans fats (hydrogenated or partially hydrogenated vegetable oil) to cook their French fries, but his team will need to collect data for several more years before they will have enough statistical power to see if removing trans fats de-fangs the fries.

The Trouble with French Fries:

This is not the first study to tag French fries as trouble-makers. Years ago, nutrition scientists from Italy, Great Britain and the US noted that potatoes have a high glycemic index. That is, they tend to raise blood sugar quickly. But potatoes also contain many nutrients, so it can be difficult to estimate how eating them will affect a person’s health.

To learn more about that, scientists recruited 4,400 middle-aged and older Americans and followed them up for eight years (American Journal of Clinical Nutrition, July 2017). They filled out a detailed dietary survey at the start of the study. Most of them ate potatoes frequently, at least twice a month, and a third of the volunteers ate potatoes three or more times a week.

Just eating potatoes didn’t seem to make a difference. Those who indulged in French fries at least twice a week, however, were about twice as likely to die during the study as those who never ate them. Perhaps the large amount of trans fat often found back then in French fries (and potato chips) is partly to blame.

Italian Potato Eaters Not at Risk:

We are not sure exactly why French fries seem so risky. The Italian researchers recommended that similar investigations be carried out in larger groups of people. Would this association be confirmed? They then followed through on this recommendation themselves. Their subsequent study examined potato consumption in Southern Italy (Journal of Nutrition, Health & Aging, June 2018). The 2,442 volunteers were no more likely to die during the 11-year study if they ate lots of potatoes than if they ate just a little. We don’t have information on how the potatoes were prepared, though. Probably, the Southern Italians were not scarfing down French fries.