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Abstract & Commentary
Synopsis: Reducing weight and moderate daily exercise prevented the development of type 2 diabetes in subjects with impaired glucose tolerance.
Source: Tuomilehto J, et al. N Engl J Med. 2001;344: 1343-1350.
The incidence of diabetes is increasing worldwide at an alarming rate. This study was done to see whether type 2 diabetes can be delayed or prevented by interventions that affect lifestyles of subjects at high risk.
The study group assigned 522 middle-aged, overweight subjects (172 men and 350 women), mean age 55 years, mean body mass index 31, with impaired glucose tolerance, to either an intervention group or to a control group. The intervention group received individualized counseling aimed at reducing weight, total intake of fat and saturated fat, and increasing intake of fiber and physical activity. An oral glucose tolerance test was performed annually; the diagnosis of diabetes was confirmed by a second test. The mean duration of follow-up was 3.2 years. The study was stopped early because of the significant difference between the 2 groups.
The mean weight loss between baseline and the end of the first year was 9.24 lbs in the intervention group and 1.7 lbs in the control group; the net loss by the end of year 2 was 7.7 lbs in the intervention group and 1.7 lbs in the control group (P < 0.001 for both comparisons between groups). The cumulative incidence of diabetes after 4 years was 11% in the intervention group and 23% in the control group. During the trial, the risk of diabetes was reduced by 58% in the intervention group. The reduction in diabetes was directly associated with changes in lifestyle. Tuomilehto and colleagues concluded that type 2 diabetes can be prevented by changes in lifestyles of high-risk subjects.
This was an "intention to treat" protocol and it is remarkable that none of the subjects who reached 4 or 5 of the goals developed diabetes (49 in the intervention group and 15 in the control group).
The subjects in the intervention group were given detailed advice about how to achieve a 5% reduction in weight loss, to reduce the total fat intake to less than 30% of the energy consumed, and an intake of saturated fat to less than 10% of the energy consumed, an increase in fiber to at least 15 g per 1000 calories, and to perform moderate exercise for 30 minutes daily. They were also advised to eat whole grain bread, vegetables, fruits, low fat milk, and meat and vegetable oils rich in monounsaturated fatty acids.
The individualized exercise prescriptions included walking, jogging, aerobic ball games, and swimming to increase cardiorespiratory fitness. Individualized circuit-type resistance training sessions were offered to improve functional capacity and strength. The rate of participation in these sessions varied from 50-85% at the various centers. This appears to be an exercise program that improves aerobic fitness and would reduce muscle cell fat content.
Comment by Ralph R. Hall, MD, FACP
Two recent papers emphasize the importance of lifestyles and their relevance to the development of type 2 diabetes. The first paper by Salmeron and colleagues in analyzing the Nurses’ Health Study found a strong correlation between the intake of trans fatty acids and the incidence of type 2 diabetes.1 The diet prescribed in this study does lower the trans fatty acid intake. It is similar to the DASH diet,2 (and, if you will, a diet similar to the Mediterranean diet). The Lyon Heart study using the Mediterranean diet resulted in a 70% reduction in "all cause" mortality due to a reduction in coronary heart disease without lowering the LDL cholesterol.3
In another paper, Toth and colleagues found a greater relationship between exercise endurance capacity (VO2 Max) and glucose disposal rates than from either total or regional adiposity.4 The more fit the individual the better the glucose disposal rate and the less the insulin resistance.
There has been a trend toward emphasizing that just a little exercise is better than none and ultimately influencing people to reduce the amount of exercise they do. There has been the fear that if we asked patients to do more intense exercise that they would be intimidated and do less. The results of these studies suggest that we must prescribe exercise so that it is intense enough to have a training effect (increasing VO2 max).
Using diet and exercise we have the tools to drastically reduce the incidence of a disease that not only is costing billions of dollars but leads to suffering, early death and disability from heart disease, blindness, and renal failure. There is a great need and opportunity to use these tools more effectively than we have done in the past.
Imagine your patients’ response to being prescribed a Mediterranean diet rather than a Step One National Cholesterol Education Program diet.
1. Salmeron J, et al. Am J Clin Nutr. 2001;73:1019-1026.
2. Sacks FM, et al. N Engl J Med. 2001;344:3-10.
3. de Lorgeril M, et al. Circulation. 1999;99:779-785.
4. Toth MJ, et al. Am J Physiol Endocrinol Metab. 2001; 281:E113-E121.