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Your Low-Carb Diet May Increase—Not Decrease—Diabetes Risk, New Study Suggests

Not all low-carb diets are created equal, and research says that quality matters over quantity.
FACT CHECKED BY Samantha Boesch

If you want what you eat (and don't eat) to help prevent diabetes, then you've most likely heard that you should stick to a diet that's low in carbohydrates. However, a new study has found that not all low-carb diets have the same effect when it comes to lowering the risk of this disease.

The research from the study, which was presented at the American Heart Association's Scientific Sessions conference, per Merck Manuals, involved attempting to find a connection between low-carbohydrate diets and the risk of Type 2 diabetes. And what they found was that the overall quality of carbohydrates, fat, and protein may matter more than the quantity itself.

What the study found about low-carb diets and diabetes

woman eating yogurt

The study used information that was collected from 203,541 adults who did not initially have diabetes and took part in either the Nurses' Health Study, Nurses' Health Study II, or the Health Professionals Follow-Up Study that took place between 1984 and 2017. The studies tracked participants for up to 30 years while requiring them to fill out questionnaires regarding their eating habits every four years.

When those behind the study attempted to determine the amount of carbohydrate consumption, they did so by considering the daily percentage of total energy that came from carbohydrates, as well as from protein and fat. Although U.S. Dietary Guidelines say that a person's diet should consist of 45% to 65% of energy intake from carbohydrates, there were some participants in the study whose diets were only made up of around 40% carbs.

Beyond that, the people who were eating diets lower in carbohydrates, and included animal protein as well as fat, had a 35% higher risk of type 2 diabetes. That percentage rose to 39% when they also weren't getting enough whole grains. On the other hand, participants who were eating a low-carb diet that included protein and fat that came from plant-based food had a 6% lower risk of Type 2 diabetes. They also had a 15% lower risk when they ate fewer refined carbohydrates and less sugar.

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What experts say about these findings

eating a salad

"To prevent the risk of Type 2 diabetes for generally healthy people without prediabetes or diabetes, the quantity of carbohydrates might not matter as much as the quality of the protein, fats, and carbs," said lead study author Yeli Wang, a research fellow in the department of nutrition at the Harvard T.H. Chan School of Public Health in Boston.

"I do agree that not all low-carb diets have an equal impact on our health," Justine Chan, MHSc, RD, CDE, registered dietitian and certified diabetes educator tells Eat This, Not That! "This is because the quality of the foods you're eating also matters."

When it comes to why an animal-based, low-carb diet might increase the risk of diabetes, Chan explains that "saturated fats can increase insulin resistance, which plays a key role in the development of type 2 diabetes."

As for a plant-based, low-carb diet, Chan says, "I suspect the fiber and the resistant starch found in plant foods provide anti-inflammatory benefits, which help to reduce the risk of diabetes. Fiber also slows down the release of glucose into the bloodstream, thereby reducing blood sugars."

Desirée O
Desirée O is a freelance writer who covers lifestyle, food, and nutrition news among other topics. Read more about Desirée
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