Prevention of type 2 diabetes by lifestyle intervention: a Japanese trial in IGT males

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Abstract

Prevention of type 2 diabetes by intensive lifestyle intervention designed to achieve and maintain ideal body weight was assessed in subjects with impaired glucose tolerance (IGT). Male subjects with IGT recruited from health-screening examinees were randomly assigned in a 4:1 ratio to a standard intervention group (control group) and intensive intervention group (intervention group). The final numbers of subjects were 356 and 102, respectively. The subjects in the control group and in the intervention group were advised to maintain body mass index (BMI) of <24.0 kg/m2 and of <22.0 kg/m2, respectively, by diet and exercise. In the intervention group, detailed instructions on lifestyle were repeated every 3–4 months during hospital visits. Diabetes was judged to have developed when two or more consecutive fasting plasma glucose (FPG) values exceeded 140 mg/dl. A 100 g oral glucose tolerance test was performed every 6 months to detect improvement of glucose tolerance. The subjects were seen in an ordinary outpatient clinic.

The cumulative 4-year incidence of diabetes was 9.3% in the control group, versus 3.0% in the intervention group, and the reduction in risk of diabetes was 67.4% (P < 0.001). Body weight decreased by 0.39 kg in the control group and by 2.18 kg in the intervention group (P < 0.001). The control group was subclassified according to increase and decrease in body weight. The incidence of diabetes was positively correlated with the changes in body weight, and the improvement in glucose tolerance was negatively correlated. Subjects with higher FPG at baseline developed diabetes at a higher rate than those with lower FPG. Higher 2 h plasma glucose values and higher BMI values at baseline were also associated with a higher incidence of diabetes, but the differences were not significant. Subjects with a low insulinogenic index (ΔIRI/ΔPG 30 min after an oral glucose load) developed diabetes at a significantly higher rate than those with a normal insulinogenic index.

Comparison of the BMI data and incidence of diabetes in five diabetes prevention studies by lifestyle intervention revealed a linear correlation between the incidence of diabetes and the BMI values, with the exception of the DaQing Study. However, the slope of the reduction in incidence of diabetes in the intensive intervention groups was steeper than expected simply on the basis of the reduction of BMI, suggesting that the effect of lifestyle intervention cannot be solely ascribed to the body weight reduction.

We conclude that lifestyle intervention aimed at achieving ideal body weight in men with IGT is effective and can be conducted in an outpatient clinic setting.

Introduction

Primary prevention of type 2 diabetes mellitus has been attracting a great deal of interest recently [1], [2], [3], because a dramatic increase in the number of diabetic patients in the world portends a serious problem in the future. Type 2 diabetes is on the rise throughout the world, and it is estimated that the number of cases of diabetes will be doubled in the 15 years from 1995 to 2010 [4]. It was about 100 million in 1994, and is expected to be 230 million in 2030 [5]. Its prevalence in adults was 4.0% in 1995 and is expected to increase to 5.4% in 2025 [6]. The increase in diabetes is particularly striking in developing countries, but there has also been a steady increase in developed countries such as in the United States and Japan [7], [8].

Despite progress in methods of treating diabetes, vascular complications, both microangiopathy and macroangiopathy, are common, and they are important causes of morbidity and mortality in diabetic patients [9], [10]. Diabetes is becoming a major burden on the national health care expenditure [11], and it is no wonder that WHO stresses the importance of preventing diabetes [12]. Several trials have shown a beneficial effect of intervention by lifestyle manipulation or drug therapy in persons with impaired glucose tolerance (IGT) in decreasing the incidence of type 2 diabetes [13], [14], [15], [16].

Type 2 diabetes has also been increasing in Japan, where its prevalence increased by six- to seven-fold over the past 30 years [17]. Japanese people have been the least obese in developed countries, but their mean body mass index (BMI) is tending to gradually increase [18], and the increase in type 2 diabetes is a concern.

Since 1984 we have been following subjects with mild abnormalities of glucose metabolism detected by screening in a general health checkup program, and they have been examined regularly by repeated oral glucose tolerance tests (OGTT) [19], [20]. In this paper, we report that the development of diabetes can be significantly prevented by intervention in lifestyle designed to achieve and maintain the ideal body weight of each individual during an observation period of 4 years in subjects with IGT.

Section snippets

Subjects

Since 1983 the Health Medical Center in Toranomon Hospital has been conducting a health-screening program, mostly for government employees. We randomly selected subjects with a fasting plasma glucose (FPG) value below 140 mg/dl and a 2-h plasma glucose (2hPG) value after a 100 g glucose load of between 160 and 239 mg/dl on 100 g OGTTs from among examinees in 1990–1992. This 2hPG level roughly corresponds to the 140–199 mg/dl range on the 75 g OGTT, and thus the subjects had IGT according to the WHO

Baseline characteristics and follow-up

Table 1 shows the baseline characteristics of the control group and the intervention group. Body mass index (BMI), history for diabetes among first-degree relatives, prevalence of low early insulin response on the OGTT (ΔIRI/ΔPG (30 min) <0.5 μU/ml/mg/dl), and serum triglyceride, total cholesterol, and HDL-cholesterol levels, did not differ significantly between the two groups. The plasma glucose and insulin levels during the 100 g OGTT were very similar in the control and intervention groups (

Discussion

Individuals with IGT are a high-risk group for the development of type 2 diabetes. In this study males with IGT were selected to assess the effect of lifestyle intervention on the incidence of diabetes. The intervention was individualized according to the current lifestyle of each subject and was designed to achieve and maintain the optimal BMI by appropriately adjusting the amount and composition of meals and increasing physical activity. Lifestyle intervention resulted in significant

Acknowledgments

The authors are grateful to Dr. Akihiro Isogawa for technical assistance in the statistical analyses.

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