Following a low-carbohydrate diet led to improved blood glucose control in people with untreated prediabetes or type 2 diabetes, according to a new study published in the journal JAMA Network Open.
Whether people with diabetes should be following a low-carb diet is one of the longest-running debates in the diabetes community, and this conversation is often clouded by confusion about what a low-carb diet actually means. But recent studies point to some impressive benefits linked to following a low-carb diet. One study found that following a low-carb vegan diet (yes, that’s possible) led to weight loss and improved blood glucose control in people with diabetes. Another study found that for people with both type 2 diabetes and nonalcoholic fatty liver disease (NAFLD), following a low-carb, high-fat diet led to both improved blood glucose control and liver benefits. Low-carb diets have also been shown to contribute to remission of type 2 diabetes, and they may also help improve kidney function in people with type 2.
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For the latest study, researchers were interested in how following a low-carb diet affected blood glucose control in people with an untreated A1C level (a measure of long-term blood glucose control) between 6.0% and 6.9%. Based on the latest guidelines, a normal A1C level is below 5.7%, while an A1C level between 5.7% and 6.4% indicates prediabetes. An A1C level of 6.5% or higher indicates diabetes.
The study included 150 participants with an A1C level between 6.0% and 6.9% — 108 of them women — with an average A1C level of 6.16% and an average age of 58.9 at the beginning of the study. Participants were randomly assigned to follow either their normal diet or a low-carb diet for six months, with 75 participants in each group. There were 142 participants still left in the study at both of the follow-up intervals, after three months and six months — two participants dropped out of the low-carb group, and six participants dropped out of the usual-diet group.
At the beginning of the study, by coincidence, the low-carb group — which hadn’t yet started on a low-carb diet — had a slightly higher average caloric intake than the usual-diet group, at 1,890 calories compared with 1,789 calories each day. The low-carb group got an average of 44% of its calories from carbohydrate, compared with 42% in the usual-diet group.
Reduced body weight, A1C in low-carb group
Over the course of three months following their assigned diets, the low-carb group had a lower average caloric intake than the usual-diet group — 1,447 compared with 1,701 calories each day. They also got just over half as much of their calories from carbohydrate — 23%, compared with 42%, on average. After six months, the average daily caloric intake in the low-carb group was 1,439 compared with 1,757 in the usual-diet group, and the low-carb group got an average of 25% compared with 42% of their daily calories from carbohydrate.
After three months, A1C had dropped by an average of 0.23% in the low-carb group, compared with 0.07% in the usual-diet group, for a difference of 0.16%. After six months, A1C had dropped by an average of 0.26% in the low-carb group, compared with 0.04% in the usual-diet group, for a difference of 0.23% — a significant improvement over the usual-diet group. The low-carb group also lost an average of 6.4 kilograms (14.1 pounds) of body weight over the course of the study, compared with an average loss of 0.5 kilograms (1.1 pounds) in the usual-diet group — for an average greater body weight reduction of 5.9 kilograms (13.0 pounds). This weight loss corresponded to a drop in waist circumference, indicating that it was largely due to the loss of unhealthy body fat.
The researchers found that following a low-carb diet, without taking any glucose-lowering medications, was linked to a significant improvement in blood glucose control among study participants. But since this diet also led to greater weight loss, it was unclear whether the low-carb diet itself — or the weight loss it caused — was responsible for the beneficial effect on blood glucose. “This diet, if sustained, might be a useful dietary approach for preventing and treating type 2 diabetes, but more research is needed,” the researchers concluded.
Want to learn more about low-carb diets and diabetes? Read “Low Carb Myths and Facts,” “Low-Carb for Diabetes,” and “Scrumptious Lower-Carb Lunches.”