Prescribing low-carb diets for type 2 diabetes: many approaches can work

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As the number of doctors, dietitians, and other diabetes specialists interested in carb restriction continues to grow, questions inevitably arise. How many carbs per day should people with diabetes eat? Are targets for protein and fat intake necessary, or can people be advised to eat as much as they need to feel full?

Recently, a group of Australian researchers explored these questions in a systematic review of studies on low-carb diets in people with type 2 diabetes:

Diabetes, Obesity & Metabolism: An evidence‐based approach to developing low‐carbohydrate diets for type 2 diabetes management: a systematic review of interventions and methods

This was an extensive review of 41 intervention studies, including 18 randomized trials, totaling 2135 participants altogether. Results from one of the studies weren’t included in the analysis due to high risk of bias.

Although some studies didn’t provide detailed data beyond the carbohydrate prescription, the overall composition of the diets varied widely:

  • Carbohydrates: 13 studies restricted carbs to less than 50 grams per day. Another 14 restricted carbs somewhere between 50 to 130 grams per day — a fairly broad range across studies. The remaining 13 studies restricted carbs to less than 50 grams per day initially, and then individualized carb intake depending on progress.
  • Protein: Of the 26 studies that reported a protein prescription, 10 allowed unrestricted protein, 12 specified high protein (>25% of calories), and 4 specified moderate protein (15-25% of calories).
  • Fat: Of the 20 studies that reported a fat prescription, 18 specified high or unrestricted fat, and 2 specified low fat.

The researchers assessed changes in blood glucose levels, hemoglobin A1c values, and diabetes medications as the main study outcomes. Additionally, they looked at improvements in other health markers like waist size, fasting insulin, triglycerides, and HDL cholesterol levels.

The verdict? In all 40 studies, low-carb diets were found to be both safe and effective for managing diabetes, despite the large differences in macronutrient intakes. This demonstrates that even modest carb restriction is beneficial for people with type 2 diabetes, and that consuming more protein and fat doesn’t impair blood sugar control.

Importantly, though, the research team didn’t discuss which interventions had the most dramatic effects on diabetes outcomes. Although we don’t have strong supportive data, it seems less likely that someone whose goal is diabetes reversal would be able to achieve this by eating 100 grams of carbs per day. In fact, restricting carbs to less than half that amount might be needed.

On the other hand, the researchers noted that dietary interventions only work if people can stick with them long term. While it’s true that many people enjoy eating very-low-carb diets, it may not be realistic for everyone with diabetes.

Addressing both blood sugar response and personal preferences is key to creating a truly individualized, successful low-carb lifestyle.


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What you need to know about diabetes

GuideThis page gives you an overview of what you need to know about diabetes. It will also link you to more information and, importantly, to practical guides that will help you learn what to do about having diabetes.