186. Diabetes Prevention Programme

In March 2015, NHS England announced the Diabetes Prevention Programme (DPP) which is a joint initiative with Public Health England (PHE) and Diabetes UK (1).The object is to achieve a significant reduction in the number of people with Type 2 Diabetes (T2D) which is expected to be about 4 million if no action is taken. It is claimed that there have been well-designed trials conducted in Finland, the USA, Japan, China and India which show that reductions of up to 60% can be obtained in adults at high risk by means of intervention programmes to encourage changes in lifestyle.

The justification has been developed by NICE. The initial proposals were subject to severe criticisms by specialists in the treatment of T2D (2). For example great emphasis was placed on the importance of weight loss and exercise in spite of limited evidence in support of this strategy. But this was in conflict with the drugs recommended which actually promote weight gain.

As a consequence substantial amendments were made and a revised consultation document was issued (3). The guidelines are set out in a document entitled “Type 2 diabetes in adults” (4). In addition there is whole raft of appendices.

In view of the importance of developing a policy which will successfully control this key public health issue, it is worth analyzing the DPP carefully.

The Rationale

T2D is defined as a:

“condition of insufficient insulin production often exacerbated by insulin resistance, the primary treatment for which is weight loss and exercise. Pharmacological measures to increase insulin sensitivity or to increase insulin release can be added to lifestyle interventions, but insulin therapy may eventually be needed by the majority of people as their insulin secretion declines.”

Subsequently it goes on to explain that:

“The underlying disorder of type 2 diabetes is usually that of a background of insulin insensitivity where the body is unable to respond to normal levels of insulin, and insulin deficiency where the pancreas is unable to secrete enough insulin to compensate for this resistance. Insulin insensitivity is usually evidenced by excess body weight or obesity, and is exacerbated by overeating and inactivity. It is commonly associated with raised blood pressure, a disturbance of blood lipid levels, and a tendency to develop thrombosis. This combination is often recognised as ‘metabolic syndrome’, and is associated with fatty liver and abdominal adiposity (increased waist circumference). Insulin deficiency is progressive over time, such that the high glucose levels usually worsen relentlessly over a period of 30 years, requiring continued escalation of blood glucose lowering therapy.”

This really is quite remarkable because the insulin resistance is caused by the excessive production of insulin. It is obvious that those responsible for these proposed guidelines have a very limited perspective. While it is true that Type 1 Diabetes (T1D) is the result of insufficient insulin production because of damage to the pancreas, there seems to be a failure to appreciate that T2D is a totally different disease. The fundamental issue with T2D is excessive levels of glucose in the blood. This in turn stimulates the production of extra insulin which is needed to cope with the large amounts of glucose. While this may be perceived as a requirement for more insulin, it is inevitable that if more insulin is supplied it will exacerbate the insulin resistance, which contributes to the ill-health. It really does not take a genius to work out that if there is a reduction in the blood glucose then there should be a corresponding reduction in the requirement for insulin to be produced. The level of blood glucose is determined by the diet and therefore it follows that alteration to the diet is the obvious solution to the problem.

The Solution

Although the main emphasis in the DPP was on the use of drugs to treat T2D there is one chapter which is devoted to “Lifestyle and non-pharmacological management”. This concludes that:

“there was little new evidence to warrant any change to previous views in this field. The major consensus-based recommendations from the UK and USA emphasise sensible practical implementation of nutritional advice for people with type 2 diabetes. Management otherwise will concentrate on principles of healthy eating (essentially those for optimal cardiovascular risk protection), and reduction of high levels of free carbohydrate in foods that may cause hyperglycaemia in the presence of defective insulin secretory reserve”.

Here again, note the term “defective insulin secretory reserve” where the underlying assumption seems to be that the body should be able to cope with whatever is thrown at it. Would it not be much more sensible to regard a diet which produced excessive glucose in the blood as toxic? Obviously this question never arose because it is certainly not addressed in the current official recommendations which are to:

“Emphasise advice on healthy balanced eating that is applicable to the general population when providing advice to adults with type 2 diabetes. Encourage high-fibre, low-glycaemic-index sources of carbohydrate in the diet, such as fruit, vegetables, wholegrains and pulses; include low-fat dairy products and oily fish; and control the intake of foods containing saturated and trans fatty acids”.

It goes on to state that:

“If people are currently gaining weight, weight maintenance is advantageous”.

Finally some suggestions for future research are presented on the grounds that:

“Type 2 diabetes is associated with obesity, and lifestyle interventions including diet and physical activity are thought to be useful in helping to control the condition and improve patient outcomes such as reducing the risk of long-term complications and increasing quality of life. Low carbohydrate diets have been a source of discussion over the past two decades and there is much debate regarding its effectiveness and safety in controlling blood glucose levels, particularly in the longer-term. Specifically, there is little consensus on the optimal intake of daily carbohydrates, where the risk of adverse effects such as hypoglycaemia is minimised. A randomised controlled trial addressing this clinical question would help to provide a better understanding of the effects of low carbohydrate diets on diabetes control and maintenance to inform appropriate management strategies”.

During the consultation period a number of pertinent comments were made (5). It was pointed out that there was no reliable evidence to support a recommendation to reduce SFA therefore the advice to consume low fat dairy produce could not be justified. The response was:

“Thank you for your feedback. It was not within the scope of the guideline to update the evidence review on dietary advice therefore it is not possible to make changes to this section”.

When it was suggested that longer-term trials need to be undertaken to test the long-term efficacy and safety of low carbohydrate diets, the reply was exactly the same.

Essentially what we have is a passing reference to “Diet and lifestyle” which simply goes along with the current approach. The response to the comments made during the consultation exercise reveals that there are no plans to change things as they are. Presumably this is accurately reflected in what appears on the NHS Choices website (6) which proffers the following advice on how to cope with T2D.

For diet, the strategy is to increase the amount of fibre and to reduce fat, especially SFA. Specific advice includes:

Increase consumption of foods such as wholegrain bread and cereals
Choose foods that are low in fat – replace butter, ghee and coconut oil with low fat spreads and vegetable oil

Choose skimmed and semi-skimmed milk, and low fat yoghurts

If you have a BMI of 30kg/m²or over you should lose weight by gradually by reducing your calorie intake and becoming more physically active. Losing 5-10% of your total body weight over the course of a year is considered to be a realistic initial target.

With respect to exercise for adults who are aged between 19 and 64 years, it is recommended that there should be a minimum of:

150 minutes (2 hours and 30 minutes) of “moderate-intensity” aerobic activity, such as cycling or fast walking, a week, which can be taken in sessions of 10 minutes or more, and
muscle-strengthening activities on two or more days a week that work all major muscle groups (legs, hips, back, abdomen, chest, shoulders and arms).

Conclusion

Although there is relatively little emphasis on diet and lifestyle, it is evident that there is heavy reliance on weight loss. This seems to be unduly optimistic, especially as there are no plans to review the existing dietary recommendations, which have not exactly been a howling success. On the face of it, the chances of success do not appear to be high so I will be doing a more detailed critique in subsequent blogs.

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