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Prevention of type 2 diabetes by intensive lifestyle intevention designed to achieve and maintain ideal body weight was assessed in male subjects with impaired glucose tolerance (IGT).

• men who had a fasting plasma glucose (FPG) value below 140 mg per dL and a two hour plasma glucose (2hPG) value after a 100 g glucose load of between 160 and 239 mg per dL on 100 g oral glucose tolerance test (OGTT).  

• previous history of diabetes
• diagnosed or suspected malignant neoplasm
• diagnosed or suspected disease of the liver, pancreas, endocrine organs or kidney
• ischemic heart disease or cerebrovascular disease or a history of such disease.

Recruitment -- male subjects with impaired glucose tolerance (IGT) were recruited from a health-screening program (mostly for government employees) at the Torannomon Hospital, Japan.

Design --randomized intervention; one in five subjects were randomly assigned to the intensive intervention group; the other four were assigned to the standard intervention (control) group.

Blinding used (if applicable)--not applicable

Intervention (if applicable)

Following a 1 year run-in observation period, male subjects with IGT were randomly assigned in a 4:1 ratio to a standard intervention (control) group and intensive lifestyle intervention group in an outpatient clinic setting.

All study participants were informed of the pathogenesis and risk factors of type 2 diabetes and the importance of a healthy lifestyle aimed at achieving and maintaining ideal body weight (most desirable body mass incex (BMI) defined as 22 kg per m²⁾.  The subjects in the control group and in the intervention group were advised to maintain BMI of <24.0 kg/m² and <22.0 kg/m², respectively, by diet and exercise.

Control Group

• Subjects with a BMI >24kg per m² were instructed to take 5-10% smaller meals than previously, and to increase their physical activity to lose weight.
• Subjects with a BMI<24kg per m² were told to avoid gaining weight by dieting and exercise.
• The above objectives were explained every six months when the subjects came to the hospital.

Intervention Group

• Subjects with a BMI >22kg per m² after individually beginning informed of their desirable body weight (calculated on the basis of their height so that the BMI = 22 kg per m²) were told to weigh themselved at least once a week at home and reduce their weight at a rate of 0.5 to 1.0 kg per month.
• Subjects with a BMI less than 22kg per m² were advised to maintain their current weight.
• In the intervention group, detailed instructions on lifestyle (diet and exercise) were repeated every three to four months during hospital visits. The lifestyle intervention was tailored to each subject.
• Food Exchange Lists (Japan Diabetes Association) was used as the basis for instructions for diet and other diet instructions included: reduction of portion sizes by about 10 percent, family support, and to eat out no more than once a day.
• For physical activity, inclusion of moderate exercise, such as walking 30-40 minutes a day was recommended.
• Changes in body weight and achievement of desirable body weight were considered to be measures of the overall success of the intervention.

Development of diabetes was the primary outcome. When diabetes developed, the subjects were excluded from the study and followed up as a ordinary type two diabetic patient.  

Statistical Analysis

• The Kaplan-Mayer method was used to express the cumulative incidence of diabetes.
• The percentage of subjects who followed the diet and exercise instructions were not calculated.
• Results were presented as means±standard deviation (S.D.)
• Significance established as P<0.05

Timing of Measurements

• 100g OGTT was performed every 6 months to detect improvement of glucose tolerance
• Blood samples were collected before and 30, 60, 90, 120 and 180 minutes after the glucose load and the plasma glucose and insulin levels were measured.
• Urinalyses (protein, glucose and casts), blood counts (RBC, WBC, platelets, hemoglobin, etc), blood chemistry studies (total cholesterol, HDL-cholesterol, triglycerides, BUN, creatinine, uric acid, etc) were performed every 6 months.
• Blood pressure and body weight were recorded at every hospital visit.
• ECG and chest X-ray were examined once a year.

Dependent Variables

• development of diabetes--defined by fasting plasma glucose (FPG) values exceeded 140 mg per dLon two consecutive tests performed at an interval of two weeks or less
• improvement of glucose tolerance--defined as when the OGTT results converted to non-IGT
• change in body weight
• achievement of ideal body weight

Independent Variables

• intensive lifestyle intervention or standard intervention (control)

Control Variables

 

Initial N: did not report initial number of subject but stated that the 5.6 percent were lost during the one year observation period in the control group and 4.7 percent were lost in the intervention group; resulting in the final number below

Attrition (final N):  control group: 356; intervention group--102 (all male)

Age: no specific mean or medians, baseline age breakdown provided

 

Age (years) (%)	Control Group (N=356)	Intervention Group (N=102)
30s	18 (5.1)	4 (3.9)
40s	177 (32.9)	31 (32.3)
50s	192 (53.9)	58 (56.9)
60s	29 (8.1)	7 (6.9)

Ethnicity: Japanese

Other relevant demographics: 85% of follow-up subjects were government employees.

Anthropometrics mean baseline body mass index (BMI) for all subjects: 24.0 kg/m².  Baseline BMI did not differ significantly between control and intervention group;  BMI for control group- 23.8±2.5kg per m² mean (± SD); for intervention group- 24.0±2.3kg per m².

Location: Japan

 

Other Findings

• At baseline, there were no significant differences between the control group and the intervention group in any of the following: percentage of family history of diabetes, serum triglyceride, total cholesterol, HDL-cholesterol, blood pressure (systolic and diastolic), plasma glucose, insulin levels, and the 100 g OGTT.
• The cumulative four-year incidence of diabetes was 9.3 percent in the control group and 3.0 percent in the intervention group, and the reduction in risk of diabetes was 67.4 percent (P<0.001).
• Decrease in weight in the intervention group was significantly greater than the control group during the four year follow-up period (P<0.001)     (-2.18±1.63kg vs. -0.39±1.42kg, respectively).
• The control group was subclassified according to increase and decrease in body weight during the four year follow-up period; Group A--body weight increased by 1.0kg or more; Group B--body weight remained unchanged; Group C--body weight decreased by 1.0kg or more.
•  The cumulative four-year incidence of diabetes was 14.7 percent in Group A, 10.6 percent in Group B, and 4.3 percent in Group C (P<0.01 Group A vs. Group C).  Thus, the incidence of diabetes among subjects in the control group who gained weight (1.0kg or more) was significantly higher than among those whose body weight decreased by 1.0kg or more.
• The rate of improvement in glucose tolerance from IGT to non-IGT after 4 years was 53.8 percent in the intervention group and 33.9 percent in the control group (P<0.001).
• The rate of improvement in glucose tolerance in the control group increased significantly from Group A to Group C (12.5 percent vs. 47.6 percent, respectively) (P<0.008), paralleling the decreases in body weight.
• Subjects with a higher FPG at baseline (11.8 percent) developed diabetes at a higher rate than those with a lower FPG (5.4 percent; P=0.04) and the incidence of diabetes was higher in those with higher 2hPG and higher BMI values at baseline, but the differences were not statistically significant.

 

 

 

Lifestyle intervention individualized according to the current lifestyle of each subject and was designed to achieve and maintain the optimal BMI (BMI <22 kg/m²) by appropriately adjusting the amount and composition of meals and increasing physical activity resulted in significant decreases in body weight and the cumulative incidence of diabetes over a four year follow-up period. The results are consistent with other studies demonstrating the beneficial effect of lifestyle intervention in preventing or delaying the occurrence of type 2 diabetes in subjects at high risk of diabetes.

The incidence of diabetes was positively correlated and the improvement in glucose tolerance was negatively associated with the change in body weight. Changes in body weight were associated with the incidence of diabetes not only in the comparison between the intervention and the control group, but between the subgroups within the control group classified according to changes in body weight.

The authors concluded that lifestyle intervention that included diet and exercise components aimed at achieving ideal body weight in men with IGT is effective and can be conducted in an outpatient clinic setting. Comparisons with previous diabetes prevention studies, the slope of reduction in incidence of diabetes in the intensive intervention group was steeper than expected simply on the basis of the reduction of BMI, suggesting that lifestyle intervention (ie, restriction of energy intake and increase in physical activity) must have decreased the risk of diabetes independently of the reduced body weight, presumably by increasing insulin sensitivity.

• statistical analysis other than Kaplan-Meyer method for cumulative incidence of diabetes not discussed
• ? generalizability; subjects were all male and Japanese (desirable BMI for Japanese is 22 kg/m²);
• epidemiological studies have suggested ethnic differences in genetic susceptibility to type 2 diabetes
• fat distribution (waist circumference, waist/hip ratio, and visceral fat accumulation were not investigated in the present study; may be strongly associated with diabetes