Should You Cut Your Carbs If You Have Prediabetes? Here’s What New Research Suggests


Low-carb diets have been trending for a while, and they’ve always been pretty controversial. On the one hand, many people share anecdotal stories about how low-carb fad diets like keto helped them lose weight. But on the other hand, super restrictive diets like these cut out food groups that are super healthy, like whole grains, fruit and starchy vegetables.

Not only does this make them hard to follow, but also it can make it hard to get enough fiber and meet your nutrient needs.

However, new research published on October 26, 2022, in Diabetes and Endocrinology found that there might be some benefits to reducing your carb intake if you have diabetes or are at risk. Here’s what you need to know.

What the Study Found 

For this randomized clinical trial, the researchers recruited 150 participants between ages 40 and 70 in New Orleans, LA. Seventy-two percent of the participants were women, and 59% of participants were Black. They took several biomarkers related to diabetes such as hemoglobin A1C, fasting blood glucose and weight. Then, researchers divided participants into a low-carb dietary intervention group or a control group. The control group was instructed to consume their usual diet.

This intervention portion of the study was six months long, and was split into two phases for the intervention group. For the first three months, diets were limited to 40 grams of net carbs per day; for months four through six, diets were limited to 60 grams of net carbs per day. It’s important to note that the study used net carb intake, meaning the number of total carbs minus the carbs from fiber. The rationale for net carbs is that fiber is not digested into usable energy for our cells beyond our gut, so it does not have the same impact on blood glucose as other non-fiber carbs.

After the six-month trial, the low-carb diet intervention group had significant reductions in hemoglobin A1C levels (about 0.23%), fasting blood glucose levels (about 10.3 mg/dL) and body weight (about 5.9 kilograms on average or roughly 13 pounds).

What It Means

The 2020-2025 Dietary Guidelines for Americans recommends that about 45 to 65% of calories come from carbs. For a person on a 2,000-calorie diet, this would be around 225 to 325 grams of carbs daily. By comparison, the carb intake limits set by the study are quite low. However, using net carbs might have allowed participants to enjoy more high-fiber foods like leafy greens, legumes and berries to help make their diet more balanced and easier to follow. That said, the carb limits they set would still be very challenging to follow for most adults. And with such a small sample size, larger-scale research needs to be done to support their findings for the general population.

“The key message is that a low-carbohydrate diet, if maintained, might be a useful approach for preventing and treating Type 2 diabetes, though more research is needed,” said lead author Kirsten Dorans, assistant professor of epidemiology at Tulane University School of Public Health and Tropical Medicine in a media release.

The Bottom Line 

New research out of Tulane University School of Public Health found that those who limited their intake to 40 to 60 grams of net carbs per day had significant reductions in hemoglobin A1C, fasting blood glucose and body weight compared to those who consumed their usual dietary pattern with no restrictions. While these findings add to a growing base of research about the benefits of lower-carb diets of diabetes, more research is needed to substantiate their findings. If you have diabetes, prediabetes or are at a higher risk, focus on keeping carb intake consistent throughout the day,regardless of the amount that you consume. Also, talk to your health care team to identify the right carb intake for you before making any drastic lifestyle changes.