There is good evidence that a low-carb diet helps people with diabetes improve blood sugar control, reduce the need for diabetes medications, and lose weight.
A 2018 Diabetes Canada position statement titled “Low-Carb Diets for Adults with Diabetes: A Quick Review” recommended that healthy low-carb diets be considered a dietary pattern for people with type 1 or type 1 diabetes. type 2.
However, there is limited evidence on whether a low-carb diet is beneficial for blood sugar control in people with prediabetes or diabetes who are not treated with medication.
A new study from Tulane University in Louisiana adds to the evidence base. His findings: A low-carb diet, if maintained, can be a useful tool in preventing type 2 diabetes.
The randomized clinical trial, published Oct. 26 in the journal JAMA Network Open, investigated the effect of a low-carb diet versus standard dietary advice on hemoglobin A1c levels.
A hemoglobin A1c (HbA1c) test measures your average blood sugar level over the past three months. It is used to diagnose prediabetes and diabetes, as well as to guide diabetes management.
The Canadian Diabetes Association considers an HbA1c of 6.0 to 6.4% in the prediabetes range. According to the American Diabetes Association, an HbA1c of 5.7 to 6.4 percent indicates prediabetes. Both organizations use an HbA1c of 6.5% or higher to diagnose diabetes.
The six-month trial recruited 150 people, with an average age of 59, with HbA1c levels in the range of prediabetes and diabetes (6.0 to 6.9 percent) who were not treated with diabetes medications. Most participants (130) had prediabetes.
Half of the participants followed a low-carb diet and received regular dietary counseling throughout the study. Supplementary foods were provided (eg, olive oil, nuts, canned vegetables, low-carb bars and shakes) to help people adhere to the diet.
The net carb goal was less than 40 grams per day for the first three months, then less than 60 grams per day for the last three months. Net carbs are grams of total carbs minus grams of fiber, carbs that our bodies don’t digest.
Recommended foods included non-starchy vegetables, fish, poultry, lean meat, eggs, olive oil and other unsaturated oils, unsweetened nuts and seeds, nut butters , avocados and a moderate consumption of cheese as well as unsweetened Greek yogurt and milk. Fruits, cereals, beans and lentils were limited or avoided.
Fat accounted for half of the calories consumed by low-carb dieters, mostly heart-healthy monounsaturated and polyunsaturated fats (eg, olive oil, avocado, nuts, seeds).
Participants in the usual diet group received written information on standard dietary advice; they did not receive ongoing dietary recommendations.
Findings, implications, limitations
After six months, participants in the low-carb group had greater decreases in HbA1c compared to those in the usual diet group. They also had significantly lower fasting blood sugar and lost more weight.
These findings are important for people with prediabetes, who are estimated at 22% of Canadians.
The reduction in HbA1c was modest, but it was a similar decline to that seen in the historic diabetes prevention program. This large-scale trial showed that people with prediabetes could prevent or delay the onset of type 2 diabetes by losing 7% of their initial body weight through dietary changes (low fat, low calorie ) and physical activity.
One limitation of the current study: it was unable to assess whether the reduction in HbA1c was caused by the low-carb diet itself or by calorie restriction with weight loss.
Due to the length of the study, it’s also unclear if the participants were able to stick to the low-carb diet long-term, or if the diet affected progression to type 2 diabetes.
Although these new findings suggest a low-carb diet is an option for people with diabetes or prediabetes, the researchers said it should be studied further.
Considerations if Going Low-Carb
Talk to your doctor before making any major dietary changes. This is especially important for people with diabetes who are taking medication.
If you’re taking a diabetes medication that increases your risk of low blood sugar, reducing your carbohydrate intake may require your doctor to adjust your medication.
A low carb diet is not for everyone. Some people struggle to stick with it long term, and others report feeling unsatisfied without carbs in a meal.
If you’re considering trying a low-carb diet to manage blood sugar, consult a dietitian who can determine an appropriate carbohydrate goal and design a healthy meal plan that matches your food preferences and meets daily nutritional needs.
Leslie Beck, a dietitian in private practice in Toronto, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD
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