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Exercise and diet can prevent type 2 diabetes



?It is now accepted that overt type 2 diabetes marks an advanced stage of a disease process that has been present for many years and will have already caused irreversible damage to the patient's vascular system. Three papers analysing interventions have recently been published, demonstrating the importance of lifestyle changes in the prevention of type 2 diabetes.

The first paper is a systematic review and meta-analysis of pharmacological and lifestyle interventions to prevent or delay type 2 diabetes in people with impaired glucose tolerance.

The authors found 21 trials met the inclusion criteria and that 17 randomised, controlled trials, with a total of 8,084 participants, reported results in enough detail to be analysed.

The results showed that lifestyle changes, oral hypoglycaemics and the anti-obesity drug orlistat all reduced the number of people progressing to diabetes. The numbers needed to benefit were 6.4 for lifestyle change, 10.8 for oral hypoglycaemic drugs, and 5.4 for orlistat.

The authors conclude that lifestyle intervention is at least as effective as drug treatment.

These findings support those of the Finnish Diabetes Prevention study's long-term follow-up results.

The original study looked at 522 people with impaired glucose tolerance, of whom two-thirds were women. They were randomised to limited advice on exercise and diet, or a tailored, intensive programme of diet, weight reduction and exercise. The population started with a mean BMI of 31 kg/m2. The intensive lifestyle modification group were instructed to lose 5 per cent of their body weight, limit fat intake to less than 30 per cent of daily calories, limit saturated fat intake to less than 10 per cent of daily calories, increase fibre intake to at least 15g per 1,000 calories, and to exercise moderately for at least 30 minutes per day.

The intensive lifestyle modification group showed a relative risk reduction of 58 per cent.

Participants who were still free of diabetes at four years were followed up for a further three years. During the post-intervention follow-up, the relative risk reduction of the incidence of diabetes was 36 per cent. The total follow-up relative risk reduction was 43 per cent. The authors conclude that lifestyle intervention in people at high risk of developing type 2 diabetes results in sustained lifestyle changes and reduced incidence of diabetes, even after the intervention had finished.

The dramatic results stratified according to how closely participants adhered to their targets. It would seem sensible for these simple and modest measures to be widely adopted, but to date no research has been able to demonstrate sustained lifestyle changes in the general population from primary care intervention.

The DREAM study examined whether treatment with either rosiglitazone or ramipril would prevent impaired glucose tolerance progressing to diabetes.

The study included 5,269 people with impaired glucose tolerance and/or impaired fasting glucose, who were randomised, double blind, to either rosiglitazone (4mg/day for two months then 8mg/day) or placebo, or ramipril 15mg/day or placebo. Over a follow-up with a median of three years, the primary outcome measures were diabetes or death.

At the end of the study ramipril did not significantly reduce the risk of diabetes, but rosiglitazone showed a 14.4 per cent relative risk reduction. Although this is encouraging, the case selection and design of the study has been questioned.1 The study also showed that the rosiglitazone group developed significantly more heart failure (14 patients compared with two in the placebo group), despite being a low-risk population. There were also more cardiovascular events in the treatment group.

These studies give a consistent message about the power of lifestyle intervention to prevent or delay the progression from impaired glucose tolerance to diabetes. Impaired glucose tolerance is already a late phase in the chain of events that ends in diabetes, but it is likely that lifestyle intervention may be extrapolated to confer protection against earlier pathological processes. Intervention with drugs does not offer superior results to lifestyle change, and may be associated with unwanted effects.

Gillies CL, Abrams KR, Lambert PC, et al. Pharmacological and lifestyle interventions to prevent or delay type 2 diabetes in people with impaired glucose tolerance: systematic review and meta-analysis. BMJ 2007;334:299

Lindstrom J, Ilanne-Parikka P, Peltonen M, et al. Sustained reduction in the incidence of type 2 diabetes by lifestyle intervention: follow-up of the Finnish Diabetes Prevention Study. Lancet 2006;368:1673-9

Gerstein HC, Yusuf S, Bosch J, et al. Effect of rosiglitazone on the frequency of diabetes in patients with impaired glucose tolerance or impaired fasting glucose: a randomised controlled trial. Lancet 2006;368:1096-105

Bosch J, Yusuf S, Gerstein HC, et al. Effect of ramipril on the incidence of diabetes. N Engl J Med 2006;355:1551-62


Dr Matthew Lockyer
GP, Suffolk and hospital practitioner in diabetic medicine

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