Excess weight gain is a key risk factor responsible for the development of around 90% of cases of type 2 diabetes. A majority of people with type 2 diabetes have a body mass index (BMI) >25kg/m2 and about half have a BMI >30kg/m2. Among those with a BMI >35kg/m2, 20% of all men and 11% of women have been diagnosed with diabetes.
Weight management is a fundamental element in the management of type 2 diabetes. While modest sustained weight loss of 5–10% can prevent its onset, obesity guidelines in Scotland, in recognition of the increases in the prevalence of obesity, recommend a weight loss target of >15–20% for those with a BMI >35kg/m2 with obesity-related complications such as type 2 diabetes.
THE CHALLENGE OF WEIGHT LOSS
In routine diabetes care, it is very challenging to achieve weight loss. With conventional dietary advice, average weight loss is usually only in the region of 3–5%, and many of the older medications used to manage diabetes (sulphonylureas and insulin) favour further weight gain. Hence, few individuals achieve a weight loss of ≥15kg (or ≥15%).
Bariatric surgery, which results in substantial weight loss and remission of diabetes, is one treatment option and is indeed recommended by UK guidelines for those who are obese and have type 2 diabetes. However, surgery is unattractive to many who are fit enough to undergo the procedure, side effects are common, and it is unlikely to be feasible within the already constrained resources of the NHS. There is therefore little prospect of it being offered to the majority of people with type 2 diabetes.
FORMULA DIETS
An alternative approach is the use of liquid formula diets as a total diet replacement (TDR). This can achieve substantial weight loss, up to 15% or more. A non-surgical approach is more attractive to the general public. The diets are popular and widely used outside healthcare settings. But historical reluctance by medical staff to support their use means that they have seldom been offered as part of diabetes care.
There is already considerable evidence regarding the safety and efficacy of low energy formula diets for achieving weight loss in the management of type 2 diabetes. Safe, nutritionally complete, formula diets were first introduced in the 1980s and, since then, many studies have consistently found that they can achieve weight loss of about 15kg. This does not seem to be dependent on the calorie content, as similar weight loss is achieved with 820kcal/day, which may be more palatable, and 300–400kcal/day. Importantly, results for people with type 2 diabetes are equally good.
PROVING EFFECTIVENESS
While providing proof of concept, these studies were small and undertaken in a research setting. The question remained whether this approach would be equally effective when delivered on a larger scale and within primary care, where the majority of people with type 2 diabetes are managed.
The Diabetes Remission Clinical Trial (DiRECT), was carried out in primary care, to discover if the use of a structured weight management programme that included a low energy formula diet (825–853kcal/ day) could be a practical option for achieving ≥15kg weight loss and remission of type 2 diabetes of less than 6 years’ duration. An initial 12–20 weeks of TDR (soups and shakes) were followed by carefully managed food reintroduction and then long term weight loss maintenance. The intervention was delivered at GP practices by either a specially trained practice nurse or a community dietician.
A mean weight loss of 10kg was maintained after 1 year with striking effects on remission of type 2 diabetes: 46% overall achieved remission (glycated haemoglobin (HbA1c) <48mmol/mol off antidiabetic medication for at least 2 months). With weight loss of >15kg, 86% were no longer diabetic. In the control arm of the study, only 4% of participants (who had continued with usual diabetic care) achieved enough weight loss for remission, and none lost 15kg.
IN SUMMARY
Use of formula diets results in more rapid weight loss than conventional approaches, and improvements in blood glucose levels are seen quickly. Both these factors are highly motivating, as is the potential for remission and remaining free of diabetes medications. A top priority for people with type 2 diabetes is finding a cure, or a means of putting their diabetes into long term remission.
'Use of formula diets results in more rapid weight loss than conventional approaches, and improvements in blood glucose levels are seen quickly.’
Formula diets, used for a period as a TDR, allow the individual to step away from food for a period of time. This is often welcomed, since decisions over what and how much to eat are removed. Formula diets are reasonably palatable and, in DiRECT, many people chose to continue with the TDR for longer than the minimum required period.
Some side effects can be experienced. In DiRECT, the most common were constipation, feeling cold, dizziness and headache. In the main, these were described as mild-to-moderate and transient. It is important to reintroduce meals gradually and provide ongoing support for weight loss maintenance. Weight loss maintenance is crucial in sustaining remission.
Concerns that rapid weight loss will lead to greater weight regain are not supported by evidence. There was no difference in weight regained at 144 weeks of follow-up between people who had followed a 12-week rapid weight loss programme and those who had undertaken a 36-week gradual programme. Supportive follow-up is important to maximise long term weight stability.
While they will not appeal to everyone, formula diets are an acceptable, safe and effective option which can achieve the benefits of substantial weight loss and remission of type 2 diabetes seen following bariatric surgery.
Wilma Leslie, Research Associate, University of Glasgow
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