Updated 30 November 2017

Is a low-carb diet really the answer for type 2 diabetes?

Should those with type 2 diabetes follow a low carb diet? Our dietitians weigh in.

Type 2 diabetes is characterised by the resistance to the function of insulin – and eventually insulin insufficiency.

Insulin is a hormone that is released in response to raised blood sugar levels. Blood sugar levels are influenced by several factors such as stress, activity and by the type and quantity of the carbohydrates we consume.

The question we are addressing is if a low carbohydrate diet is the best way to optimally manage blood sugar levels.

What is a low carbohydrate diet?

The term ‘‘low carbohydrate diet’’ is problematic due to the controversy in the scientific community on the amount of carbohydrate allowed in the diet. A low carbohydrate diet ranges between 30 and 30g of carbohydrate per day, consisting of largely “complex” carbohydrates such as naturally occurring whole grains, fruits and vegetables.

The very low level of 30g of carbohydrate is easily reached by consuming e.g. 1 medium sized fruit providing 20g of carbohydrate and 3 baby potatoes providing 15g.

The other problem with a low carbohydrate diet is that one size doesn't fit all. A woman weighing 50kg who consumes 80g of carbohydrate cannot be compared with a 90kg man consuming the same amount. It might be sufficient for the woman, but definitely not for the 90kg man. 

The main management goals of type 2 diabetes are:

  • Achieving glycaemic control with blood sugar levels within given ranges
  • Obtaining and maintaining an ideal body weight
  • The control of additional risk factors such as cholesterol or blood pressure in order to prevent or lower the risk of cardiovascular disease (CVD)

The advantages of a low carbohydrate diet with regards to diabetes management:

  • Research has shown short-term improvements in blood sugar control, weight loss and CVD risk.
  • A low carbohydrate diet also leads to the avoidance of refined carbohydrates such as white bread, white rice and particularly sugar, as well as sugar-sweetened beverages (SSB), which are generally associated with increased sugar levels, risk for obesity and CVD.

Disadvantages of a low carbohydrate diet:

  • A possible lack of fibre and nutrients such as thiamine (Vitamin B1), vitamin C and magnesium in the diet has been reported based on a computer-generated analysis of four popular diets, including the Atkins, LEARN, Ornish, and Zone.
  • The question whether the diet is affordable and sustainable as a lifestyle
  • An increased risk of hypoglycemia (low blood glucose levels) in people who are treated with insulin and glucose-lowering drugs. (Before commencing a low carbohydrate diet, inform your health care professional in case adjustments to your medication need to be made.)
  • These diets tend to include foods with the biggest carbon footprint – therefore large-scale adoption  will increase greenhouse gas emissions.
  • When studies compare the effects of a variety of carbohydrate intakes on diabetes management, higher carbohydrate diets tend to fare better than low carbohydrate regimes in terms of weight loss, glycaemic control, lipid concentrations, blood pressure, and compliance with treatment.


So, what diet is best for diabetics? SEMSDA (Society from Endocrinology, Metabolism and Diabetes of South Africa) recommends an individualised approach. A health professional should consulted to compile a sustainable eating pattern based on the person's lifestyle, culture, budget constraints and food preferences.

Carbohydrate management is a key factor in diabetes management and it is vitally important that both the type and amount of carbohydrate consumed in the diet be addressed.

Image credit: iStock


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Diabetes expert

Dr. May currently works as a fulltime endocrinologist and has been in private practice since 2004. He has a variety of interests, predominantly obesity and diabetes, but also sees patients with osteoporosis, thyroid disorders, men's health disorders, pituitary and adrenal disorders, polycystic ovaries, and disorders of growth. He is a leading member of several obesity and diabetes societies and runs a trial centre for new drugs.

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