Background: Weight loss and increased physical exercise reduce the risk for diabetes in people with impaired glucose tolerance. Randomized trial evidence on the effect of these interventions on people without impaired glucose tolerance is lacking.
Objective: To examine the influence of a comprehensive intervention program on the risk for developing diabetes in men without impaired glucose tolerance and in a post hoc subgroup analysis by baseline cigarette smoking status.
Design: Randomized, controlled trial.
Setting: 22 clinical centers for the Multiple Risk Factor Intervention Trial (MRFIT).
Participants: 12,866 men age 35 to 57 years at risk for cardiovascular disease were randomly assigned to either a special intervention or usual care group and followed for 6 to 7 years; this report focuses on 11,827 men without diabetes or impaired glucose tolerance at entry for whom follow-up glucose measurements were available.
Measurements: Cardiovascular disease risk factors, fasting blood glucose levels, and diabetes medication history were assessed before randomization and annually.
Intervention: Men in the special intervention group were counseled to change diet (reduce saturated fat, cholesterol, and calorie intake), to stop smoking, and to increase physical activity. Blood pressure was treated more intensively in the special intervention group than in the usual care group.
Results: 11.5% of the special intervention group and 10.8% of the usual care group developed diabetes over 6 years of follow-up (hazard ratio, 1.08 [95% CI, 0.96 to 1.20]). The special intervention-usual care hazard ratio for diabetes was 1.26 (CI, 1.10 to 1.45) among smokers (63%) and 0.82 (CI, 0.68 to 0.98) among nonsmokers (37%). These estimates differed significantly (P = 0.0003). Weight gain after smoking cessation and the use of antihypertensive drugs may have counterbalanced the beneficial effect of the lifestyle intervention for the special intervention group smokers, while the lifestyle intervention was beneficial among nonsmokers.
Limitations: Principal findings are based on a post hoc subgroup analysis.
Conclusions: In nonsmokers, an intervention program that included nutrition counseling to produce reductions in weight, serum cholesterol, and (along with antihypertensive medication) blood pressure reduced the risk for diabetes.