Do French Fries Really Increase the Risk of Type 2 Diabetes
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| Balanced vs refined carbohydrate foods including potatoes, fries, rice, and whole grains. |
For decades, the humble potato has been at the center of nutrition debates. Often criticized by low-carb advocates, it is frequently dismissed as little more than a source of starch. However, new research suggests that the potato's reputation may be shaped more by how it is prepared than by the vegetable itself.
A landmark study published in BMJ in 2025 highlights what researchers call the "Potato Paradox." The findings show that the metabolic effects of potato consumption depend almost entirely on preparation methods and the foods consumed alongside them. The key takeaway is clear: French fries are associated with an increased risk of type 2 diabetes, while boiled, baked, and mashed potatoes do not show the same association.
The Link Between French Fries and Diabetes Risk
Researchers found that, overall, every three weekly servings of potatoes, regardless of preparation method, were associated with a modest 5% increase in the rate of type 2 diabetes.
However, when cooking methods were analyzed separately, the results revealed a significant difference.
The French Fry Factor
Consuming just three servings of French fries per week was associated with a 20% higher risk of developing type 2 diabetes.
This increase was substantially greater than that observed for other forms of potato consumption.
Cooking Methods Make All the Difference
One of the study's most important findings is the distinction between deep-frying and more traditional cooking methods.
Type 2 Diabetes Risk by Preparation Method
| Preparation Method | Statistical Risk of Type 2 Diabetes |
|---|---|
| French Fries | 20% Increase |
| Boiled, Baked, or Mashed Potatoes | No Significant Increase |
These findings suggest that the question is not only "what we eat" but also "how we prepare it."
When potatoes are boiled, baked, or mashed, they retain their nutritional value without producing the same metabolic effects associated with frying.
What Should You Eat Instead?
The study also examined the effects of replacing potatoes with other carbohydrate-rich foods.
Whole Grains: The Best Alternative
Replacing three weekly servings of potatoes with whole grains was associated with an 8% reduction in type 2 diabetes risk.
When French fries specifically were replaced with whole grains, the risk reduction increased to 19%.
Even replacing boiled or baked potatoes with whole grains was associated with a 4% lower risk.
White Rice Is Not a Better Option
Contrary to popular belief, replacing potatoes with white rice did not improve metabolic health.
The study found that swapping potatoes for white rice was associated with an increased risk of type 2 diabetes. Researchers suggest that this may be due to white rice's high glycemic index, which can trigger rapid spikes in blood sugar while providing fewer nutrients and less fiber than whole potatoes.
Nutritional Value of Potatoes
Potatoes provide several essential nutrients, including:
- Dietary fiber
- Vitamin C
- Magnesium
- Complex carbohydrates
However, potatoes are also rich in starch and have a relatively high glycemic index.
This means that their carbohydrates are rapidly broken down into glucose, leading to a quick rise in blood sugar and insulin levels.
According to the editorial accompanying the study, non-fried potatoes remain nutritious foods that can fit into a healthy and environmentally sustainable diet.
The issue appears to arise when potatoes are deep-fried. Researchers suggest that the combination of high-temperature oil and starch may create a less favorable metabolic profile that outweighs the vegetable's nutritional benefits.
A Large-Scale Study
The conclusions of this research are supported by an exceptional amount of data.
Key Numbers
- Follow-up period: 1984 to 2021
- More than 205,000 U.S. healthcare professionals included
- 22,299 documented cases of type 2 diabetes during follow-up
Methodology
- Participants had no history of diabetes, cardiovascular disease, or cancer at the start of the study.
- The majority of participants were of European ancestry.
- Dietary habits were assessed every four years using detailed food questionnaires.
Study Limitations
Despite its impressive size, several limitations should be considered.
An Observational Study
The research identified statistical associations but cannot prove that French fries directly cause type 2 diabetes.
A Specific Population
Because most participants were U.S. healthcare professionals of European descent, the findings may not be fully applicable to all populations worldwide.
Additional Lifestyle Factors
Although researchers adjusted for numerous variables, unmeasured lifestyle factors could still have influenced the results, including sedentary behavior and broader dietary habits associated with frequent fast-food consumption.
Conclusion: Are Potatoes Back on the Menu?
The study delivers a nuanced message. Potatoes should not be viewed as a single, uniform food category. Their health effects depend heavily on how they are prepared.
The evidence suggests that French fries are the primary potato product associated with an increased risk of type 2 diabetes, with a 20% higher risk linked to three weekly servings.
In contrast, boiled, baked, and mashed potatoes showed no significant increase in risk.
To support long-term metabolic health, researchers recommend prioritizing whole grains as a primary carbohydrate source and consuming potatoes in moderation while limiting fried varieties.
When prepared using simple cooking methods, potatoes can remain part of a balanced, nutritious diet that supports chronic disease prevention.
References
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Potatoes and risk of type 2 diabetes
Ibsen DB, Zhang Y. BMJ, 2025. -
Scientists discovered something surprising about french fries and diabetes
ScienceDaily, June 3, 2026.