Development of Type 2 Diabetes among People Participating in a Program To Promote Healthy Behaviors

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The summary below is from the full report titled "Incidence of Type 2 Diabetes in the Randomized Multiple Risk Factor Intervention Trial." It is in the 1 March 2005 issue of Annals of Internal Medicine (volume 142, pages 313-322). The authors are G. Davey Smith, Y. Bracha, K.H. Svendsen, J.D. Neaton, S.M. Haffner, and L.H. Kuller, for the Multiple Risk Factor Intervention Trial Research Group.

What is the problem and what is known about it so far?

Type 2 diabetes (adult-onset diabetes) interferes with the body's ability to store energy from food. The result is high levels of blood sugar. Over time, high blood sugar levels lead to complications such as blindness, kidney failure, and heart disease. Many people with type 2 diabetes have moderately high levels of blood sugar for years before the levels reach true diabetes levels and symptoms begin. This condition is called abnormal glucose tolerance or prediabetes. Diet and exercise can prevent or delay the development of type 2 diabetes in people with prediabetes. However, no definitive studies have shown whether healthy behaviors also reduce type 2 diabetes in people without prediabetes.

Why did the researchers do this particular study?

To find out whether a program to promote healthy diet and exercise behavior would reduce the development of type 2 diabetes in people without prediabetes.

Who was studied?

11,827 men without prediabetes who were participating in a large study called the Multiple Risk Factor Intervention Trial (MRFIT). The main purpose of the MRFIT study was to examine the effect of changes in health behaviors on the development of heart disease.

How was the study done?

The researchers assigned men in the study to receive either usual health care or a special program that involved counseling to reduce fat and calorie intake, stop smoking, and increase physical activity. Men in the special program also received more intensive treatment of blood pressure than men in the usual care group. The researchers followed the men for 6 to 7 years to see who developed type 2 diabetes. They examined results separately for smokers and nonsmokers.

What did the researchers find?

Similar numbers of men in both groups developed type 2 diabetes. However, nonsmokers who participated in the special program were less likely to develop diabetes than those who received usual care.

What were the limitations of the study?

The researchers did not plan the separate analyses of smokers and nonsmokers from the beginning of the study, so these findings are preliminary. In addition, the study included only men, so the findings might not apply to women.

What are the implications of the study?

A special program to promote healthy diet and exercise behaviors can reduce the development of type 2 diabetes for nonsmokers without prediabetes. The special program did not reduce type 2 diabetes among smokers without prediabetes, and this emphasizes the need to maintain adequate weight control after stopping smoking.