A low-carbohydrate diet may help people at risk for diabetes lower their blood glucose (sugar) without medication, a new study suggests.
Researchers found that people who followed a low-carb diet for six months saw a greater drop in hemoglobin A1c (HbA1c), a marker for blood glucose levels, compared to people who ate their usual diet.
“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,” lead author Kirsten Dorans, ScD, an assistant professor of epidemiology at Tulane University’s School of Public Health and Tropical Medicine in New Orleans, said in a news release.
The study was published Oct. 26 in JAMA Network Open.
Around 37 million Americans have diabetes, of which 90–95% of cases are type 2 diabetes, according to the Centers for Disease Control and Prevention (CDC).
In addition, more than 1 in 3 American adults have prediabetes, where blood glucose levels are elevated but not high enough for a person to be diagnosed with diabetes. Prediabetes increases the risk of developing type 2 diabetes, heart disease and stroke.
The new study included 150 people aged 40 to 70 years old who had untreated prediabetes (HbA1C of 6.0% to 6.9%). Of these, 59% were Black, 41% white and 7% Hispanic.
Researchers randomly assigned people to follow either a low-carbohydrate diet or their usual diet for six months.
During the first three months, people in the low-carb diet group ate fewer than 40 grams of carbohydrates a day. For the next three months, they ate fewer than 60 grams of carbohydrates a day.
Low-carb foods include meats, eggs, cheeses, nuts, seeds, and vegetables such as olives, celery, carrots, peppers, broccoli, cauliflower, and tomatoes.
People in the low-carb diet group people also participated in frequent behavioral counseling sessions and received recipes for low-carb meals. Study staff also provided them with key low-carb foods such as nuts, olive oil, and other products to help them make their own meals.
People who followed their usual diet were provided with standard written information about healthy diets and were given the chance to participate in monthly educational sessions unrelated to diet.
Researchers followed up with participants after 3 months and after 6 months. Ninety-five percent of participants completed the 6-month follow-up visit.
After 6 months, people in the low-carb diet group saw an average decrease in HbA1c of 0.26 percentage points, which Dorans called “modest but clinically relevant.”
In contrast, among people following their usual diet, HbA1c decreased on average by 0.04 percentage points.
The low-carb diet group also had larger drops in fasting blood glucose levels, body weight, fasting insulin levels and waist circumference, researchers found.

Although the drop in HbA1c in the low-carb diet group was modest, it is similar to that seen in the Diabetes Prevention Program (DPP) study.
DPP is a lifestyle intervention that involves a low-fat, low-calorie diet, along with moderate physical activity and weight loss.
In that earlier study, people without diabetes who followed the program saw a 58% decrease in their risk of type 2 diabetes after almost 3 years.
Given the small number of participants and the shorter follow-up in the new study, researchers were unable to determine the impact of a low-carb diet on the risk of developing diabetes.
“Future work could be done to see if this dietary approach may be an alternative approach for type 2 diabetes prevention,” said Dorans in the news release.
Another question that will require additional research is whether the drop in HbA1c is due to the low-calorie diet itself or other factors.
At the 6-month follow-up, people in the low-carb diet group were eating about 400 fewer total calories per day on average, compared to those following their usual diet.
In addition, people in low-carb diet group lost about 13 pounds more than those in the usual diet group during the 6-month study.
“Therefore, it is unclear whether the HbA1c reduction in the low-carbohydrate dietary group is caused by the low-carbohydrate diet itself, or by the caloric restriction with weight loss,” said Dr. Qin Yang, an endocrinologist and medical director of the UCI Health Diabetes Center in Irvine, California.
One of the strengths of the new study is that none of the participants were taking medications for type 2 diabetes, such as metformin. This allowed researchers to study the impact of diet alone on blood glucose levels among people with prediabetes.
However, the researchers pointed out that the program used in this study may not work in all settings. Participants had frequent meetings with study staff to help them safely follow a low-carb diet, which may not be available to everyone.
Some health insurance plans or employers may offer similar counseling sessions with a nutritionist or dietician to help people find a diet that works for them.
While this study focused on people with prediabetes, Yang said diet is also an “essential component” for helping people diagnosed with diabetes manage their blood glucose levels.
Regular physical activity and stress management can also help people with diabetes keep their blood glucose levels within a healthy range.
“However, it is important to consult your physician for diabetes guidance and treatment options,” said Yang.
Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.
Current Version
Oct 26, 2022
Shawn Radcliffe
Edited By
Gillian Mohney
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