Risk factors

Low carb diets supported for T2D but not T1D: position statement

A low-carb diet may be beneficial and safe for some people with type 2 diabetes but there is not enough evidence to support low-carb diets for type 1 diabetes, a new position statement from Diabetes Australia advises.

Its first position statement on low carbohydrate diets comes in response to the increasingly popular but controversial weight loss method that has gained widespread media attention.

Low-carb dieting generally involves restricting carbohydrate consumption to 25% or less of total energy intake, but there are many iterations including the Atkins diet (developed by a cardiologist in 1972), the more recent Paleo diet and the ‘ketogenic’ diet, which recommends cutting carbohydrates to 5% of daily caloric intake to drive the body into ketosis.

But such diets can cause hypoglycaemia, side effects and be medically contraindicated, and there are also marked differences in the level of evidence supporting use of the diet in type 1 and type 2 diabetes, Diabetes Australia warns.

Its position statement notes that for people with type 2 diabetes there is reliable evidence showing that low-carb eating can be safe and useful for lowering average blood glucose levels in the short term (up to six months). It may also be at least as effective as a higher carb diet for long term blood glucose management. The diet can help reduce body weight and manage heart disease risk factors, it says.

However for people with type 1 diabetes, there is not enough evidence to show whether low-carb eating is safe or effective, Diabetes Australia concludes. It points to a 2018 review of evidence finding some studies showed improvements in HbA1c while others showed no effect.  And while anecdotal feedback from some people with type 1 diabetes has suggested benefits for low-carb eating, large, high-quality studies are needed to validate their long term effectiveness and safety in T1D, the statement advises.

Low-carb diets can raise the risk of hypoglycaemia for people taking insulin or other diabetes medications such as sulfonylureas, it notes. And by depleting glycogen stores in the liver, a glucagon injection given to treat severe hypoglycaemia may result in a smaller rise in blood glucose.

Therefore “before a person with diabetes starts a low-carb plan it is important that they monitor their blood glucose levels and consult their doctor/diabetes team in case changes need to be made to their medication”.

People starting a low-carb diet should also be aware that they can cause other side effects such as tiredness, headaches and nausea.

The position statement says low-carb diets are potentially unsafe and not recommended for children under 18, pregnant women and people taking  SGLT2 inhibitors, where such diets can increase the risk of diabetic ketoacidosis. They are also not recommended for people with kidney or liver failure and anyone with a history of  disordered eating.

“People interested in trying low-carb eating to help manage their diabetes are strongly encouraged to speak with a dietitian, their doctor or other health professional to obtain individualised dietary advice and work through an approach that is suitable for them.

“Diabetes Australia recognises that low-carb eating can be an effective way of reducing blood glucose levels and achieving weight loss for people with type 2 diabetes in the short term,” the statement concludes.

“However … at this stage, there is not enough evidence of benefits or safety of low-carb eating for people with type 1 diabetes.”

The position statement was developed by an Expert Advisory Working Group that included six Accredited Practising Dieticians and Dr Tony Russell, an endocrinologist at Princess Alexandra Hospital, Brisbane.

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