French Fries Versus Baked Potatoes: One Raises Diabetes Risk 20 Percent, The Other Doesn’t

Authored by Rachel Ann T. Melegrito via The Epoch Times (emphasis ours),

Potatoes have long had a bad rap for being high in carbs. A new study backs that concern—at least in part.

That weekly french fry habit could be setting you up for diabetes decades down the road. Research found that eating french fries just three times a week may significantly raise Type 2 diabetes (T2D) risk—but, surprisingly, other potato preparations showed no increased risk at all.

“Our findings suggest it’s not fair to put all potatoes in the same basket,” lead author Seyed Mohammad Mousavi told The Epoch Times.

How You Like Your Potatoes Matters

The study, led by Harvard T.H. Chan School of Public Health, tracked more than 205,000 adults across three major U.S. observational health studies for 30 years. Participants regularly reported what they ate, along with details about their health and lifestyle.

The study found that every three extra servings of potatoes per week was associated with a 5 percent increase in T2D risk. For french fries, that jump was even higher—20 percent per three servings.

In contrast, eating baked, boiled, or mashed potatoes was not associated with an increased risk, suggesting that french fries are the main driver behind the link between potatoes and diabetes.

French fries are often loaded with salt, which can raise blood pressure and trigger inflammation, increasing the risk of T2D. However, it’s more than just the fat and salt content driving the diabetes risk.

“French fries are typically deep-fried at very high temperatures, which can produce harmful compounds,” Mousavi said. One such compound is acrylamide, formed during browning and linked to inflammation, insulin resistance, and blood vessel damage.

“Due to their deep-fried nature, they [fries] are also much higher in calories than baked or mashed potatoes,” said Melissa Mitri, a registered dietitian-nutritionist and owner of Melissa Mitri Nutrition, who was not involved in the study.

The large amounts of oil used in frying also introduce trans fats, which further increase insulin resistance and inflammation. Combined with the high-temperature cooking that breaks down resistant starches, french fries become a perfect storm for blood sugar chaos.

Potatoes and T2D

Even outside of french fries, people who ate seven or more servings of potatoes per week had a 12 percent higher risk of developing T2D. The risk rose with greater intake.

While preparation plays a key role in how potatoes affect diabetes risk, it’s worth noting they still have a high glycemic index, meaning they can rapidly raise blood sugar.

Potatoes are a common source of carbohydrates, especially starch, which the body quickly breaks down into sugar. Because of this, eating potatoes can cause a sharp rise in blood sugar levels soon after a meal.

Frequent blood sugar spikes force the pancreas to release more insulin repeatedly. Over time, this constant demand can cause insulin-producing cells to wear out or stop working properly. This contributes to insulin resistance and reduced insulin production—both key drivers of T2D.

A potato’s glycemic index, which ranks how quickly and how much foods raise blood sugar levels after eating,  depends on how they’re prepared. A higher glycemic diet is associated with an increased risk of developing T2D because the foods cause a rapid and significant rise in glucose levels.

Mashed and boiled potatoes have higher glycemic indexes because cooking breaks down their structure and makes the starch easier to digest, leading to faster spikes in blood sugar.

Deep frying also softens the starch inside, but the hot oil forms a crust with some resistant starch that slows digestion. The fat in fries also helps slow down how quickly sugar is absorbed, making their glycemic index a bit lower than mashed or instant potatoes.

Using different food preparation methods can reduce potatoes’ risks:

• Chill potatoes after cooking to increase their resistant starch content, slowing digestion and causing a more balanced rise in blood sugar.
• Bake or boil potatoes with the skin to retain more fiber and micronutrients.
• Boil, bake, or roast potatoes with minimal oil instead of frying to avoid added fats.
• Air fry potatoes to reduce the formation of harmful compounds produced by deep frying.

Replacing potatoes with other carbohydrates reduced T2D risk. Swapping mashed, boiled, or baked potatoes for whole grains like pasta, bread, or farro lowered diabetes risk by 4 percent, while replacing french fries cut it by 19 percent. Substituting fries with whole grains, legumes, brown rice, or vegetables also reduced risk by 19 percent.

The only swap that increased risk was white rice, which was linked to a 3 percent higher risk of T2D. This may be because white rice has a high glycemic index. “White rice is stripped of fiber and nutrients, digests quickly, and causes sharper spikes in blood sugar,” Mousavi said.

Whole grains have fiber that slows digestion and causes smaller blood sugar spikes.

Effects Surface Years Later

Perhaps most concerning, the study found that potato intake 12 to 20 years before diagnosis had the strongest association with diabetes risk—suggesting dietary choices in your 20s and 30s could determine your health in your 50s and 60s.

Type 2 diabetes develops gradually, with insulin resistance and inflammation starting decades before symptoms appear.

Who’s Most at Risk

Even after adjusting for genetics, diet, and lifestyle, the link between french fries and diabetes remained strong. It was especially pronounced in people with higher body mass index (BMI) and in white participants.

Mitri noted that excess weight is tied to inflammation. “Someone with a higher BMI may have more difficulty responding to insulin,” she said, which can worsen insulin resistance.

“So for people with higher BMI, the same amount of potatoes may have a bigger impact on diabetes risk,” Mousavi said.

The study also found that people who ate more potatoes often took in more calories, sugary drinks, and red meat, and were less physically active—factors that can raise diabetes risk.