Prevention of type 2 diabetes

Almost three decades ago the Finnish led the way for prevention of coronary heart disease by successfully implementing the community based North Karelia project.¹ With the recent publication of their randomised controlled clinical trial of prevention of type 2 diabetes, Tuomilehto et al have now shown that effective lifestyle changes can prevent another major chronic disease of our time.²,³

Type 2 diabetes has long been linked with behavioural and environmental factors such as overweight, physical inactivity, and dietary habits.⁴ The findings from the Finnish trial confirm this link. Major lifestyle changes resulting from industrialisation are contributing to a rapid rise in diabetes worldwide, but especially in industrialising countries. An estimated 135 million people worldwide had diagnosed diabetes in 1995, and this number is expected to rise to at least 300 million by 2025.⁴ Between 1995 and 2025 the number of people with diabetes will increase by 42% (from 51 to 72 million) in industrialised countries and by 170% (from 84 to 228 million) in industrialising countries.

Diabetes exerts a huge toll in illness, death, loss of quality of life, and economic consequences at societal and individual levels.⁴ Several treatments are effective in preventing the devastating complications of diabetes, but these are suboptimally used, and the disease itself is chronic, progressive, and degenerative.⁴ Thus, the prospect that diabetes may be prevented through lifestyle changes is a call to action. Indeed, as Ovid recommended in Remedia Amoris, we should “Stop it at the start; it's late for medicine to be prepared when disease has grown strong through long delays.”

In a randomised trial of 522 middle aged, overweight people with impaired glucose tolerance Tuomilehto et al showed that lifestyle changes can reduce the risk of progression to diabetes by a striking 58% over four years.² Each person in the intervention group received individualised counselling aimed at reducing weight, improving diet (by reducing intake of total fat and saturated fat and increasing intake of dietary fibre), and increasing physical activity. The net weight loss at the end of two years was modest: 3.5 kg in the intervention group and 0.8 kg in the control group. However, the cumulative incidence of diabetes after four years was 11% in the intervention group and 23% in the control group. The reduction in the incidence of diabetes was directly associated with the changes in lifestyle. One case of diabetes was preventable for every five subjects with impaired glucose tolerance treated for five years or for every 22 subjects treated for one year.

Two earlier studies from Sweden and China showed that lifestyle interventions may delay progression from impaired glucose tolerance to diabetes.^5–7 However, the Swedish study was not randomised and the Chinese study was randomised by clinic rather than by individual. Thus, the Finnish study offers us the best evidence so far that lifestyle modification can indeed prevent diabetes. Another major study, the diabetes prevention programme is currently underway in the United States and is expected to finish next year.⁸ As the evidence for primary prevention of diabetes accumulates, we must begin thinking about how these findings can be translated into practice.

The compelling evidence that modest lifestyle changes can prevent type 2 diabetes is an enormous shot in the arm for chronic disease prevention and health promotion. Nevertheless, translating these findings into effective intervention programmes both at clinical and public health levels may be challenging. Yet this challenge pales next to that of sustaining the lifelong implementation of complex, expensive medical and therapeutic regimens to control diabetes and its complications, a challenge faced daily by ever increasing numbers of people. The appeal of lifestyle interventions is that they are inexpensive, they have few side effects, and they actually reverse the proximal factors associated with diabetes—for example, overweight, central obesity, physical inactivity, high fat and high energy diets. In the process, they also promote health in general (reduce blood pressure and lipids), empower people, make them less reliant on medicine, and—as the Finnish study showed—they also improve quality of life. Thus, focusing on lifestyle interventions truly shifts the paradigm from preventing disease to promoting health and wellbeing. Need we ask for more?

Current pandemic patterns of diabetes adversely affect the quality of people's lives and the economies of individuals, families, and nations. The Finnish study tells us unequivocally that diabetes, a devastating disease that has largely risen out of the lifestyle excesses of contemporary civilisation, can be prevented through healthy lifestyle. Nevertheless, there remain many questions: how to apply these findings in a variety of countries and settings; how to efficiently identify and target people who will benefit most from these interventions; how best to sustain these changes; and what are the appropriate roles for the clinical and public health sectors.

The clinical setting is often not sufficiently effective in delivering lifestyle changes, and many actions at the community level affect lifestyle. Thus the next step may be to test lifestyle changes through a combination of clinical and community based strategies. The challenge of planning and implementing such comprehensive community based demonstration programmes for diabetes prevention similar to those the Finnish established for heart disease in North Karelia¹ is one that we must all strive to meet.