Low-carbohydrate diets have long been a hot topic of discussion in the diabetes community. While some people claim they’re the only way to achieve ideal diabetes control, others counter that they’re unsustainable, and that their benefits are sometimes exaggerated. It doesn’t help that there isn’t any single definition of “low-carb,” so sometimes, people aren’t even arguing about the same thing.
But there has been a growing body of research on low-carb diets for diabetes, especially when it comes to their potential benefits for type 2 diabetes. In fact, sometimes, people with type 2 are able to achieve normal or close-to-normal blood glucose levels by drastically reducing carbohydrate in their diet — a situation that’s often referred to as remission. There isn’t any single definition of remission, though, so it’s important to read the details about what this means in any study or analysis.
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A new analysis of low-carb diets for type 2 shows why the definition of remission matters. By one definition, low-carb diets led to significant reduction in remission — but by another definition, they were much less effective.
Blood glucose improvements seen after six months
The new research review, published in the journal The BMJ, examined 23 studies looking at the results of low-carb diets in adults with type 2 diabetes for at least 12 weeks — sometimes much longer. A low-carb diet was defined as less than 130 grams of carbohydrate per day, or less than 26% of calories from carbohydrate. The main outcomes researchers were interested in were an A1c level (a measure of long-term blood glucose control) below 6.5%, or a fasting glucose level below 126 mg/dl, at different points in time after starting on a low-carb diet.
The researchers found that after six months, low-carb diets were associated with a significantly higher rate of diabetes remission, defined as achieving an A1c level below 6.5% with or without the use of medication. While 57% of participants following a low-carb diet achieved remission, those in the same studies who followed a control diet saw a remission rate of only 31%.
But when the definition of remission was changed to mean achieving an A1c below 6.5% without the use of medications — essentially meaning that only diet and lifestyle measures were used to achieve close-to-normal blood glucose control — a low-carb diet wasn’t nearly as impressive, with only a small, nonsignificant difference seen between the low-carb and control diet groups.
Other benefits were also seen after six months from following a low-carb diet. There were large, clinically important improvements in weight loss, triglycerides and insulin sensitivity, compared with following a standard diet. But these benefits were smaller after 12 months, in the studies where data after 12 months was available.
When the researchers compared different types of low-carb diets across different studies, they found that very-low-carb diets — defined as less than 10% of calories from carbohydrates — were less effective at inducing weight loss than less restrictive low-carb diets.
Lessons for people with diabetes
There are several potential takeaways for people with diabetes from this research review. First, the criticism that low-carb diets aren’t sustainable appears to be partially true, at least when it comes to their lasting benefits. While they led to some promising results after six months, after 12 months, the available evidence showed that these health benefits had shrunk.
Second, these studies show that if you’re going to attempt a low-carb diet for weight loss, you’re probably better off following a less restrictive diet than a very restrictive one, since you’re unlikely to be able to stick with a very restrictive one for long.
And third, these studies show that low-carb diets aren’t just silly or unhealthy fad diets. They have real, demonstrable benefits in people with diabetes, even though some of these benefits may not be sustained beyond a six-month period. But if you’re curious about whether a low-carb diet could help improve your diabetes control or your health in general, the available evidence suggests that, after talking it over with your doctor, it may be worth a try.