French Fries, but Not Baked or Boiled Potatoes, Tracked With Higher Diabetes Risk

CATEGORY: FOODS & NUTRIENTS

Every three weekly servings of French fries tracked with a 20% higher risk of developing type 2 diabetes. Baked, boiled and mashed potatoes showed no significant link. Both findings come from the same 205,107 US adults, followed for more than three decades and reported in The BMJ.¹ Type 2 diabetes is the common form, in which the body gradually loses its ability to keep blood sugar in a healthy range. For this everyday food, how it is prepared may matter more than the potato itself.

22,299 Diagnoses Across 5.1 Million Person-Years

The participants came from three long-running US projects: the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-up Study. All were free of diabetes when they joined. Every four years they filled out detailed food questionnaires, which asked, among much else, how often they ate potatoes and in what form. Across more than 5.1 million person-years of follow-up, 22,299 of them developed type 2 diabetes, with diagnoses confirmed through follow-up medical questionnaires. The analysis accounted for body weight, physical activity, smoking and other features of each person’s diet.

Whole Grains in Place of Fries, 19% Lower

Potatoes overall carried a modest link, a 5% higher rate for every three weekly servings of any kind. Fries drove nearly all of it, at 20% per three weekly servings, while baked, boiled and mashed showed essentially no association. What the potato replaced mattered as well. In substitution models, whole grains in place of three weekly servings of fries went with a 19% lower diabetes rate, and whole grains in place of potatoes generally with an 8% lower rate. White rice in place of potatoes went the other way, with a higher rate. A companion meta-analysis, which pools results from many studies, covered 13 cohorts, 587,081 people and 43,471 diagnoses of type 2 diabetes, and found the same pattern, with fried potatoes linked to a 16% higher rate.¹

Fries Rarely Arrive Alone

Nothing in this proves that fries cause diabetes. The research was observational, and what it found is an association. People who eat fries often may differ in ways a questionnaire cannot fully capture. The authors offer plausible explanations anyway. Fries are deep-fried and more calorie-dense than boiled or baked potatoes, and they tend to arrive as part of a fast-food meal. The white-rice result cuts the other way, and it shows that what a food is compared against shapes the number you get.

Two other pooled analyses fit around this one. Seven US studies following 105,531 adults found no link between potatoes overall and type 2 diabetes, but about 12% higher risk among people who ate fried potatoes more than once a week.² A 2025 systematic review of 51 observational studies also tied fried potatoes to a 16% higher diabetes risk, while tying non-fried potatoes to a small 5% increase, so the contrast between fries and the rest may be less absolute than it looks here.³

Key Takeaways

• Over more than 30 years, every three weekly servings of French fries tracked with a 20% higher risk of type 2 diabetes, while baked, boiled or mashed potatoes showed no significant association.¹
• In substitution models, whole grains in place of three weekly servings of fries went with a 19% lower diabetes rate. White rice in place of potatoes went with a higher rate.
• Observational work of this kind yields association and not causation, though a pooled analysis of 13 cohorts covering 587,081 people showed the same pattern for fried potatoes.

References

1. Mousavi SM, Gu X, Imamura F, et al. Total and specific potato intake and risk of type 2 diabetes: results from three US cohort studies and a substitution meta-analysis of prospective cohorts. BMJ. 2025;390:e082121. link
2. Djousse L, Zhou X, Lim J, et al. Potato consumption and risk of type 2 diabetes mellitus: a harmonized analysis of 7 prospective cohorts. The Journal of Nutrition. 2024;154(10):3079–3087. link.
3. Su Y, Liu X, Jiang B, et al. Potato intake and the risk of overweight/obesity, hypertension, diabetes, and cardiovascular disease: a systematic review and meta-analysis of observational studies. Nutrition Reviews. 2025;83(3):466–478. link.