Background: Lifestyle interventions that focus on weight control, increased physical activity, and dietary modifications have been shown to reduce or postpone the onset of type 2 diabetes in patients with impaired glucose tolerance. Follow-up studies lasting three to six years indicate that the relative risk of type 2 diabetes can be reduced by 30 to 67 percent. It is unclear if this reduction in risk will be sustained after discontinuing the study intervention. Lindström and colleagues followed a cohort of Finnish patients with impaired glucose tolerance to establish the long-term effect of lifestyle interventions.

The Study: The study included 522 participants, with a mean age of 55 years, who were overweight and had impaired glucose tolerance. They were randomly assigned to an intervention or control group in 1993. The intervention group (265 patients) received intensive diet and exercise counseling, with a goal of at least a 5 percent weight loss. They also were asked to limit their daily energy intake from fat to less than 30 percent with less than 10 percent from saturated fat. Other goals included at least 15 g of fiber per 1,000 kcal intake and daily physical activity for at least 30 minutes. Personal counseling sessions were offered seven times during the first year and every three months thereafter. Participants in the intervention group also were offered free access to physical training facilities. The 257 individuals in the control group were given general written and verbal health information but no specific, individualized advice.

Participants were assessed every year with a physical examination, laboratory measurements, and lifestyle intervention questionnaires. The principal outcome was the development of clinical type 2 diabetes measured by fasting blood glucose levels or a two-hour postprandial challenge.

Results: After a follow-up of seven years, 75 participants in the intervention group and 110 in the control group were diagnosed with type 2 diabetes. The incidence rates were 4.3 (95% confidence interval [CI], 3.4 to 5.4) and 7.4 (95% CI, 6.1 to 8.9) per 100 person-years in the intervention and control groups, respectively. The hazard ratio was 0.57 (95% CI, 0.43 to 0.76). In the intervention group, the cumulative incidence of diabetes was 23 percent compared with 38 percent in the control group. Ten percent of the patients in the intervention group and 27 percent in the control group did not achieve any of the pre-defined lifestyle goals. Successfully achieving the lifestyle goals was inversely related to the development of diabetes. Participants in the intervention group continued the lifestyle changes after termination of the study.

Conclusion: The interventions resulted in sustained lifestyle changes and a significant reduction in the development of type 2 diabetes for patients at high risk of developing the disease. The authors calculate that 22 individuals need to participate in lifestyle interventions for one year to prevent one case of type 2 diabetes.