Golden, crispy, and irresistible—french fries have long held a place on dinner plates and in drive-thru bags. But a new study suggests they may also come with a hidden cost: a higher risk of Type 2 diabetes.
Published in The BMJ, the research tracked more than 205,000 U.S. adults over nearly 40 years, analyzing their eating habits and health outcomes. Among potato lovers, one pattern stood out: eating three servings of french fries each week was linked to a 20% higher risk of developing Type 2 diabetes. In contrast, the same amount of boiled, baked, or mashed potatoes showed no such connection.
Type 2 diabetes—the most common form of the disease in the U.S., affecting roughly one in ten Americans—raises the risk for heart disease, stroke, and kidney damage. For lead author Seyed Mohammad Mousavi, a postdoctoral fellow at the Harvard T.H. Chan School of Public Health, the takeaway is simple: preparation matters.
“Not all potatoes are created equal,” Mousavi said. “Even less than one serving of french fries a week was associated with higher risk.”
Deep frying transforms a humble potato into a calorie-dense food, often loaded with trans or saturated fats—both of which can promote insulin resistance, weight gain, and inflammation. Over time, these factors can pave the way for Type 2 diabetes.
“When you fry potatoes, the calorie content jumps due to the fat they absorb,” explained Candida Rebello, director of the nutrition and chronic disease program at Louisiana State University, who was not involved in the study. “Frequent servings make weight gain more likely.”
The research spans an era of changing frying practices. In the 1980s, fast-food fries were often cooked in beef tallow, before shifting to partially hydrogenated oils in the 1990s—once a major source of trans fat in the U.S. diet. Today, most chains use vegetable oils such as canola, sunflower, or soybean. Regardless of the oil, Mousavi cautions that frying remains problematic.
And while baked or boiled potatoes appear safer in the data, they’re not immune to dietary pitfalls. “Think about what gets added—cheese, butter, bacon, sour cream,” said Shannon Galyean, a nutritional sciences professor at Texas Tech University. She noted that potato skins provide fiber, which helps regulate blood sugar, and that potatoes, when minimally processed, are also rich in potassium for heart health.
For those unwilling to give up fries entirely, Mousavi suggests baking them at home with healthier oils like olive or avocado. Better yet, replacing potatoes with whole grains such as farro or whole-grain bread may offer even greater protection. The study found these foods have a lower glycemic index, meaning they’re less likely to cause sharp blood sugar spikes.
Megan Mulcahy of Potatoes USA, a marketing group for the potato industry, maintains that fries can fit into a balanced diet “when enjoyed in moderation.” But experts emphasize that the broader picture—the overall quality and variety of a person’s diet—matters most.
“People don’t eat just one food,” Galyean said. “It’s the combination of what’s on the plate that shapes your health over time.”
