Eating French Fries 3 Times A Week Raises Diabetes Risk By 20%

BOSTON — French fries might be one of the most popular comfort foods around, but a major study provides more reason to avoid the common side dish. After tracking more than 200,000 Americans over several decades, researchers found that people who ate more French fries were more likely to develop Type 2 diabetes. In fact, just three extra servings of fries per week was linked to a 20% higher risk.

Meanwhile, no statistically significant association was found for baked, boiled, or mashed potatoes. The research, published in The BMJ, suggests while all potatoes are high in rapidly absorbed starch, the way they’re prepared appears to make a major difference.

Harvard Tracks 200,000+ Americans for Decades to Investigate Potato-Diabetes Link

Researchers analyzed dietary data from three large ongoing health studies involving over 200,000 U.S. medical professionals. Participants filled out food questionnaires every 2–4 years, allowing scientists to capture long-term eating patterns. Over 5.2 million person-years of follow-up, 22,299 participants developed Type 2 diabetes.

Most participants were White health professionals. As the paper notes, “more than 90% of our study population was of European ancestry,” which may limit generalizability to more diverse populations.

When the researchers looked at how often people ate different types of potatoes, they found a clear pattern:

• People who ate five or more servings of French fries a week were much more likely to develop Type 2 diabetes.
• People who ate the same amount of baked, boiled, or mashed potatoes had no meaningful increase in risk.

Even total potato intake (all types combined) was only weakly associated with diabetes risk — a 5% increase for every three extra servings a week.

Swap Fries for Whole Grains, Cut Your Risk

What happens if you trade fries for healthier carbs? That’s what the researchers tested next. They found that replacing three weekly servings of French fries with whole grains, such as brown rice, quinoa, or oats, was linked to a 19% lower risk of type 2 diabetes.

Even swapping baked or mashed potatoes for whole grains helped a little, cutting the risk by about 4%. Replacing potatoes with legumes or non-starchy vegetables also helped. But one swap actually made things worse: white rice

Potatoes naturally contain fast-digesting starch, which can cause blood sugar spikes. But frying them adds fat and may create unhealthy chemical compounds.

People who ate more fries also tended to gain weight, and that likely played a role. In fact, the researchers estimated that about half the link between fries and diabetes was explained by weight gain.

Still, the study can’t say for sure that fries directly cause diabetes. It’s based on long-term observations, not a controlled experiment. Other lifestyle factors could also be involved.

To double-check their findings, the researchers combined their results with 13 other similar studies. That larger analysis, involving nearly 600,000 people, found a similar link: eating more fried potatoes was associated with a 16% higher risk of developing diabetes.

Bottom Line: Avoid Frying Your Potatoes

This study doesn’t mean you need to swear off potatoes entirely. It just reinforces a familiar idea: how you prepare your food matters.

French fries were consistently linked to higher diabetes risk. But baked, boiled, or mashed potatoes showed no significant effect. And swapping fries for whole grains or veggies could make a real difference for your health.

Disclaimer: This article summarizes findings from an observational study and does not constitute medical advice. The study shows associations, not causation. Always consult a healthcare provider before making changes to your diet or diabetes risk management.

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