01 Nov 2018
The role and the amounts of carbohydrate in foods as part of the diet of people with type 2 diabetes is often misunderstood, and has been questioned in recent years.
Low carbohydrate diets have been regarded as an effective option for people with type 2 diabetes since the publication of the Diabetes UK Guidelines in 2011 (Dyson 2011a) with the recently updated Diabetes UK guidelines reiterating this recommendation (Diabetes UK 2018). Dietitians have a key role to play in supporting those choosing a low-carbohydrate diet to manage their nutritional needs and their type 2 diabetes.
Weight loss remains the cornerstone of type 2 diabetes management, regardless of how it is achieved, be that a low-carbohydrate, very-low-calorie or low-fat diet, or as a result of bariatric surgery. As with all areas of diet and nutrition, an individualised approach needs to take account of different tastes, lifestyles and beliefs.
More research is needed to ascertain the long-term health impacts of a low-carbohydrate diets, including on heart health.
A joint working group of The Scientific Advisory Committee on Nutrition (SACN) NHS England and Diabetes UK, with input from the BDA and Royal Colleges, is reviewing the evidence on low carbohydrate diets compared to current government advice for adults with type 2 diabetes. It is expected to report in early 2020.
This BDA policy statement (written by dietitians with clinical expertise in treating people with type 2 diabetes) is intended to state the BDA’s view point in the interim and it will be reviewed as necessary, following the publication of the joint working groups report.
This statement does not attempt to cover the needs of people with type 1 diabetes or a range of groups of people with particular needs such as children, adolescents and pregnant women. The exclusions are listed in the Background section of this Policy Statement.
The BDA believes that:
- Low-carbohydrate diets (i.e. defined as diets containing between 50g and 130g carbohydrate) can be effective in managing weight, improving glycaemic control and cardiovascular risk in people with Type 2 diabetes in the short term i.e. less than 12 months (Diabetes UK 2018). This is probably due to the accompanying reduction in energy (calorie) intake and subsequent weight loss (Diabetes UK 2018).
- More research is needed to determine the effect of long-term adherence (over 12 months) to low carbohydrate diets (as defined above) on blood glucose control (and therefore control of diabetes), and also the effect on heart health in people with type 2 diabetes.
- When people restrict their intake of carbohydrate, the relative amounts of other macronutrients (fat and protein) tend to increase. More research is needed to identify the best dietary patterns (and therefore ideal nutritional composition) to ensure both good glycaemic control and reduction in cardiovascular disease risk.
- Weight loss is still the cornerstone of management of type 2 diabetes. There is insufficient evidence to indicate that low carbohydrate diets are a superior or better approach than other strategies for weight loss and subsequent weight maintenance in the long term.
- When considering a low carbohydrate diet as an option, people with diabetes who are on certain drugs including insulin should be made aware of possible side effects such as the risk of hypoglycaemia or in rare cases ketoacidosis; it is important that individuals on such treatments should be supported by doctors and dietitians to manage such risks which may involve adjusting medication.
- People with type 2 diabetes who choose to follow a low carbohydrate diet (as defined above) should be supported by a dietitian to ensure that their diet is nutritionally adequate, enjoyable and fits in with lifestyle and cultural preferences.
The role of the dietitians in the management of people with type 2 diabetes
Dietitians are the only regulated healthcare experts in diet and nutrition and should form an integral part of the multidisciplinary team that cares for people with diabetes. They play an essential role in the support of people with diabetes – whatever their dietary preference is – including low carbohydrate approaches. This support can be individual and through the structured education programmes designed especially for people with type 2 diabetes.
The diets of people with type 2 diabetes should be individualised (NICE 2018). People are individuals with different needs, desires, tastes, lifestyles and beliefs. What works for one person with type 2 diabetes may not do so for another. It is clear that the diet of people with type 2 diabetes should have access to a dietitian in order to individualise their diet and achieve optimal glycaemic control, management of weight and risk of cardiovascular disease. The ideal amounts of carbohydrate for each individual will be affected by factors (McArdle et al. 2016) such as:
- Individual dietary preferences
- Current and future diabetes treatment
- BMI and the amount of weight that needs to be lost
- Individual glucose response
- Physical activity levels
Dietitians are both qualified and skilled to take all the above factors into account when supporting individuals with type 2 diabetes.
Whether people with type 2 diabetes choose to follow a low carbohydrate diet or not, they should be supported by a dietitian to:
- choose a variety of foods so that their diet is nutritionally complete. This includes fruit and vegetables, dairy foods, seafood, pulses, and nuts.
- moderate their intake of red meat (i.e. choose poultry in preference to red meats) and reduce intake of processed meat, sugar-sweetened foods, particularly sugar- sweetened drinks, and refined grains such as white bread.
- ensure fat intake comes mainly from unsaturated sources, whilst limiting saturated fat intake.
- include foods high in fibre
NICE (2018) recommend that all people with newly diagnosed type 2 diabetes should attend a structured education programme
Weight loss is the cornerstone of management of type 2 diabetes
Not all people with type two diabetes are overweight or obese, but in those that are weight loss remains the most effective strategy to improve glycaemic control in type 2 diabetes (Dyson 2011b). Limiting carbohydrate often serves to limit calorie intake and therefore aid weight loss (Dyson 2015). Diabetes UK (2018) recommend that to improve glycaemic control and cardiovascular disease risk, overweight or obese people with type 2 diabetes should aim for a 5% weight loss achieved by reducing calorie intake and increasing energy expenditure. There is insufficient evidence to indicate that low carbohydrate diets are superior to other strategies for weight loss and subsequent weight maintenance.
Weight management is effective at controlling glycaemia and people with Type 2 diabetes should:
- be given a choice of different evidence-based approaches to weight loss and the most appropriate dietary approach to achieve this is identified between the person with diabetes and their dietitian.
- be supported to achieve weight loss of about 5% if necessary
- be supported to maintain that weight loss
- be supported to increase their physical activity
- have access to a dietitian or other appropriately trained health care professionals who can support patients to manage their weight effectively.
Recent evidence indicates that remission from type 2 diabetes (i.e. a return to the levels of glycaemic control experienced by people without diabetes) can occur after weight loss achieved via a dietitian supported total diet replacement / meal replacement plan in the DiRECT study (Lean. 2018). A weight loss of at least 15kg was found to be associated with greatest chance of achieving remission.
As yet, the data from research into low carbohydrate diets do not show that low carbohydrate diets can result in remission from type 2 diabetes. More research needs to be done in this area.