Surgery is a treatment option which is usually only advised for patients with severe obesity (BMI>40 kg/m2), although some centres are now opting to use this in patients with a BMI>35 kg/m2 if significant co-morbidity is present.
There are two types of obesity surgery: (1) restrictive procedures and (2) combined restrictive and malabsorptive procedures.
Restrictive surgery uses bands or staples to create a stomach pouch, thereby producing a restriction in food intake.
Examples of restrictive procedures include the vertical banded gastroplasty (VBG) and the laprascopic banding procedure.
Combined restrictive and malabsorptive surgery involves a combination of restrictive surgery with bypass or malabsorptive surgery, in which the stomach is connected to the jejunum or ileum of the small intestine, bypassing the duodenum.
Roux- en-Y gastric bypass is the most commonly performed gastric bypass procedure.
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In terms of the percentage of excess weight loss, results range from 50% for restrictive procedures to 60, 70% for malabsorptive procedures.
Results from the surgical treatment of obesity provide the most convincing evidence of the benefit of weight loss in Type 2 diabetes.
The Swedish obese subjects (SOS) study is a recent prospective trial, which has demonstrated the effect of surgically induced weight loss on the incidence of diabetes mellitus (95).
The intervention consists of a surgically treated group of severely obese individuals and a matched group of weight-stable obese controls.
This study provides overwhelming evidence that weight loss not only helps reduce, treat and eliminate diabetes, but also that losing weight can prevent the onset of diabetes.
The surgically treated patients lost an average of about 60% of their body weight, with the incidence of hyperinsulinaemia and high blood glucose significantly decreased compared with the medically treated group.
For the 8 years these patients have been followed, one consistent factor has held up , weight loss maintains improvements in insulin sensitivity, helps decrease the incidence of diabetes, and effectively treats Type 2 diabetes.
Pories et al. (96) followed 608 patients who had undergone gastric bypass surgery for up to 14 years.
At 1 year, there was an average weight loss of 100 lb, which was maintained by the majority of patients at 5 years.
About 83% of the 146 patients with diabetes experienced a return to normal levels of plasma glucose, glycosylated haemoglobin and insulin.
In 152 patients with impaired glucose tolerance, more than 98% achieved normal glucose tolerance post-surgery.
It is interesting to note however that even before a large weight loss was obtained, post-surgery glycaemic control improved.
Surgical intervention requires long-term follow up to help patients adjust to the surgery and change their eating habits.
Vitamin supplementation, particularly vitamin B12, will be necessary in patients who have undergone malabsorptive surgery.
While the results from the studies of obesity surgery are impressive, as pointed out by Pinkney et al. (97), it should be remembered that no trials have been designed with diabetes as the central focus and moreover few patients on oral agents or insulin have been reported on.
There is a need therefore for more large- scale, long-term prospective studies specific to diabetes before firm conclusions can be drawn as to the role of obesity surgery in diabetes management.
CONSIDERATIONS IN MANAGING OBESITY WITHIN DIABETES CARE
It would be unusual to find the overweight patient with diabetes who has not at one time or another been advised to ‘lose some weight’. For the patient faced with the prospect of attempting to achieve this it can be helpful first of all to quantify the amount of weight loss which we now know can bring clinically
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significant benefit, i.e. 5, 10% of current body weight.
Although the results of obesity surgery provide compelling evidence that an even greater amount of weight loss can significantly reduce the need for medication and in some cases eliminate the need for any further treatment, obesity surgery will not be appropriate for or accessible to many people with diabetes.
It is important therefore that an achievable degree of weight loss is promoted and that a greater understanding of the benefits of a more modest amount of weight loss in the treatment of those with Type 2 diabetes is gained.
In addition, with many studies demonstrating weight regain following a period of weight loss, the importance of weight maintenance needs to be more strongly emphasised.
Also in advising patients to ‘lose some weight’ it is to be questioned whether current services are designed to help patients to achieve this.
Obesity, like no other condition, is considered to be solely under the control of the individual, and as such can lead to the view that there is little that can be done by the health professional to alter this.
This belief could easily impact upon the priority given to weight management within the realm of diabetes care.
It could be argued however that the ‘medical’ treatment of obesity is in effect still in its infancy, with only 50% of the health authorities surveyed in the National Audit Office report of England and Wales (1) indicating that they had a dedicated obesity strategy in place.
Weight loss achieved through changes in lifestyle is not impossible and perhaps before we dismiss weight loss as an unattainable ideal we need to consider whether we offer adequately funded, comprehensive and effective weight management programmes.
In the pharmacological management of diabetes it has already been highlighted that finding a regimen which complements both glycaemic control and weight loss is a challenge.
With a greater number of anti-obesity drugs emerging there is a need to investigate more fully their potential as front-line treatments in the management of the obese Type 2 diabetic patient.
While it is not questioned that treating hyperglycaemia reduces complications in diabetes, the long-term benefit of reacting to what is in effect the consequence of obesity rather than reacting to the obesity itself is controversial.
At a certain level of obesity, or if weight continues to increase, there will inevitably be a finite limit to the effectiveness of anti-diabetic agents and we need to consider whether a ‘reactive’ approach is the most effective in the long term.
Finally, more and more evidence is emerging to suggest that prevention strategies are extremely important, particularly since the escalation in the levels of obesity has seen a corresponding increase in the incidence of diabetes.
Indeed in Europe alone, the number of diabetic patients is predicted to increase from 16 million in 1994 to 24 million in 2010 and indicates that the 21st century will herald an astounding increase in both the financial and social costs of diabetes (98).
Impaired glucose tolerance is in effect the first stage of Type 2 diabetes and consideration must be given to (a) how such individuals can best be identified and (b) whether more rigorous intervention at this stage would be
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a more cost-effective method of tackling the impending diabetes epidemic in the long term.
Modest weight loss, for example in high-risk subjects, could help to prevent a substantial number of cases of diabetes from ever developing (64, 65).
The studies which have highlighted the benefits of weight loss in preventing progression to diabetes from IGT involved reductions in body weight of on average <5 kg.
These findings again lend credence to the message that weight loss does not have to be extensive in order to modify the risk of diabetes.
Obesity is a chronic condition that impacts greatly upon the development, the progression and the consequences of diabetes. .
Weight management should form an integral part of the management of diabetes, with a strong emphasis on the prevention of obesity. .
The traditional emphasis on achieving pharmacologically driven glycaemic control can make weight loss difficult.
Consideration should be given to the provision of a multi-skilled weight management service as part of the front- line therapy in diabetes treatment.