Original article:
Very low calorie diet (VLCD): a useful alternative in the treatment of the obese NIDDM patient. Capstick F, Brooks BA, Burns CM et al. Diabetes Res Clin Pract 1997; 36: 105-11.

Summary
The present study aimed at investigating the efficacy of a commercial very-low-calorie diet (VLCD, Modifast (r) , 425 kcal/day for 12 weeks) in 14 obese patients (mean BMI 38.7 kg/m 2 ) with Type 2 diabetes (seven subjects treated with oral hypoglycaemic agents and seven treated with insulin, mostly in combination with oral hypoglycaemic agents).
In the 13 patients who completed the study (one patient discontinued after 8 weeks because of cholelithiasis requiring cholecystectomy), body weight decreased from 108.9 to 94.5 kg, leading to a rapid and significant improvement in glucose control (reduction of HbA 1c from 8.6 to 7.1%, p < 0.02) and allowing interruption of insulin in all patients as well as a substantial reduction in the median dosage of oral hypoglycaemic tablets (from eight to two per day). Simultaneously, other risk factors such as raised arterial blood pressure and dyslipidaemia were corrected (Table I). Insulin secretion assessed during a test meal was improved after the VLCD, and fasting plas-ma alanine levels fell significantly.
The authors conclude that the short-term use of a VLCD is very effective in rapidly improving glycaemic control and promoting substantial weight loss in obese patients with Type 2 diabetes. Moreover, a VLCD increases insulin secretion and reduces substrate for gluconeogenesis. Thus VLCD treatment may improve glycaemic control by factors more than caloric restriction alone.

Comment
Most patients with Type 2 diabetes are significantly overweight, but diet-induced weight loss has been shown to markedly improve the glycaemic control of such individuals [1]. As conventional therapy combining diet and exercise usually has a poor long-term success rate, more aggressive weight reduction programmes have been proposed for the treatment of severely obese diabetic patients [1, 2]. These may include anti-obesity drugs, VLCDs and bariatric surgery. Antiobesity (anorectic) drugs may help patients to follow a restricted diet and to lose weight. However, in general, the overall efficacy on body weight and glycaemia is rather modest and the long-term safety still questionable [3].
VLCDs provide 400-800 kcal/day of high-quality protein and carbohydrate fortified with vitamins, minerals and trace elements. It is generally accepted that VLCDs are safe for use by obese diabetic patients in a medical setting closely supervised by an experienced physician, and that the numerous metabolic benefits derived from VLCD therapy outweigh the risk. Improvement in glycaemic control occurs quickly, resulting from both increased insulin action and enhanced insulin secretion. Glycaemic control improves even with only modest weight reduction, suggesting that caloric restriction plays a more critical role, at least initially, than weight loss itself, which is probably more important to maintain a sustained metabolic effect. The authors suggest that part of the action of VLCD on blood glucose control may be due to its high protein content which stimulates insulin secretion in a high glucose milieu. The effect of a VLCD and subsequent weight loss on insulin secretion is usually the opposite in non-diabetic and diabetic obese patients. Indeed, whereas both basal and post-meal plasma insulin levels are decreased after a VLCD in non-diabetic obese individuals (reflecting correction of insulin resistance), plasma insulin levels can increase in diabetic patients after weight loss. This phenomenon (which is more evident in post-meal rather than fasting conditions, as also observed in the present study) is classically attributed to the correction of chronic hyperglycaemia and hence the reduction of glucotoxicity on islet ß-cells [4]. Such a phenomenon may also contribute to increase insulin action on hepatic and muscular cells [4], in addition to other factors such as a reduction of gluconeogenic substrates (as suggested by the diminution of fasting plasma alanine levels in the present study).
The conclusions of a recent meta-analysis of 89 studies involving 1800 subjects were that dietary strategies are most effective for promoting short-term weight loss in Type 2 diabetes [5]. Diet, especially a VLCD, is very effective at obtaining short-term weight loss between 5 and 10 kg, and consequently improving HbA 1c levels. However, it was also pointed out that a number of gaps exist in the literature concerning the description of subjects, interventions or longitudinal outcomes beyond 12 months after intervention. The study of Capstick et al. only focused on the first 12 weeks of a VLCD and the authors mention at the end of the discussion that they are in the process of following these individuals over a longer period, which is of course a key issue. Although both weight gain and deterioration of glycaemic control usually tend to occur after resumption of a 'normal' diet, both happen at different rates in different individuals and can be quite gradual and modest, depending on further diet compliance.
In contrast to VLCDs, which allow an encouraging initial weight loss but do not avoid rapid weight regain, bariatric surgery has the advantages of permitting a major and sustained weight reduction. Thus, such an approach may be helpful in well-selected patients, including obese patients with Type 2 diabetes [6].

Table I: Clinical parameters in Type 2 diabetic patients at baseline and after 12 weeks of a VLCD.

The correction of weight excess after successful bariatric surgery remarkably improves glucose control parameters (fasting blood glucose and HbA 1c levels), allows interruption or reduction of insulin therapy and antidiabetic oral agents in most individuals, and probably improves the long-term prognosis of morbidly obese diabetic patients [6, 7].
In conclusion, weight loss is a major goal in treating obese patients with Type 2 diabetes, and aggressive weight reduction programmes may be used in selected patients who are refractory to conventional diet and drug treatment. VLCDs usually have a remarkable effect in the short term. It has been demonstrated that both energy restriction and weight reduction have positive effects on the glycaemic control of obese diabetic subjects. However, the long-term efficacy remains doubtful as weight regain is a common phenomenon and may be even more pronounced after a VLCD than after conventional dieting. Thus, long-term prospective studies should more precisely determine the place of such a strategy in the overall management of obese diabetic patients.

References
1. Maggio CA, Pi-Sunyer FX. The prevention and treatment of obesity. Application to type 2 diabetes. Diabetes Care 1997; 20: 1744-66.
2. Scheen AJ. Aggressive weight reduction treatment in the management of type 2 diabetes. Diabetes Metab 1998; 24: 116-23.
3. Scheen AJ. Antiobesity drugs in the treatment of NIDDM. Int Diabetes Monitor 1997; 9/1: 1-8.
4. Yki-Järvinen H. Glucose toxicity. Endocr Rev 1992; 13: 415-31.
5. Brown SA, Upchurch S, Anding R et al. Promoting weight loss in type II diabetes. Diabetes Care 1996; 19: 613-24.
6. MacDonald KG, Long SD, Swanson MS et al. The gastric bypass operation reduces the progression and mortality of non-insulin-dependent diabetes mellitus. J Gastrointest Surg 1997; 1: 213-20.
7. Scheen AJ, Paquot N, Triches K et al. Le traitement ultime du diabète de type 2: insulinothérapie intensive ou chirurgie bariatrique? In: Journées de diabétologie de l'Hôtel-Dieu. Paris: Flammarion, 1998; 81-97.

Summary and Comment:
A.J. Scheen, Liège, Belgium

Authors' reply
We agree with the general view of Dr Scheen's comments. We were able to follow up 9 of the 14 patients treated with a very-low-calorie diet (VLCD) for 12 months to monitor their long-term progress. Although there was a trend towards a return to baseline, most parameters remained better than the pretreatment values. Our results are summarized in the table below (data expressed as mean values). Whether 12 months' improvement in glycaemic control is beneficial in the long term remains to be determined.
I think a lot of clinicians would feel that even a 'temporary' remission is worth having in this group of very difficult to treat patients. At least it gives everyone a breathing space. We agree with Dr Scheen that long-term prospective studies are now required to determine the role of VLCD treatment in the management of the very obese patient with Type 2 diabetes.