In the early randomized intervention study in Malmöhus, Sweden (19
), lower rates of type 2 diabetes was found in IGT men randomized to dietary intervention compared with those who received no therapy. More recently, several trials have tested the efficacy of lifestyle intervention in prevention of type 2 diabetes.
The feasibility of diet and exercise intervention in men with IGT was assessed in another study in Malmö, Sweden (20
). Because the reference group comprised of men who did not want to join the intervention, the groups were not randomly assigned. The lifestyle intervention aimed at reducing the intake of refined sugar, simple carbohydrates, fat, saturated fat, energy, and alcohol and an increase in the intake of complex carbohydrates and vegetables. Physical activity training consisted of two weekly 60-min sessions with various dynamic activities. By the end of the 5-year study period, 11 and 29% of the men in the intervention group and reference group had developed type 2 diabetes, respectively. Overall, the progression to diabetes in these Swedish men was relatively low, even in the reference group compared with the data from the observational studies (1
). The intervention resulted in significant changes in lifestyle and physiological parameters.
In another study, 577 subjects with IGT were assigned either to a control, exercise alone, diet alone, or exercise plus diet group in Da-Qing, China (14
), using a cluster-randomized trial design. Participants were assigned to clinics for dietary intervention and were encouraged to reduce weight if BMI was ≥25 kg/m2
(61% of all participants) aiming at 23 kg/m2
; otherwise high-carbohydrate (55–65% of energy) and moderate-fat (25–30% of energy) diet was recommended. The participants were encouraged to increase their level of leisure-time physical activity by at least 1–2 “units” per day in clinics assigned to exercise intervention. One unit would correspond for instance to 30 min slow walking, 10 min slow running, or 5 min swimming. The cumulative 6-year incidence of type 2 diabetes was lower in each of the three intervention groups (41–46%) compared with 68% in the control group.
The results of the Finnish Diabetes Prevention Study (DPS) provided the first convincing evidence from a proper randomized controlled trial that type 2 diabetes can be prevented by lifestyle modification (21
). A total of 522 individuals with IGT were randomized to either an intensive lifestyle or a control intervention: during an average of 3.2 years of follow-up, type 2 diabetes incidence was reduced by 58% in the lifestyle group. The lifestyle intervention goals were 1
) reduction in weight of ≥5%, 2
) total fat intake <30% of energy, 3
) saturated fat intake <10% of energy, 4
) fiber intake ≥15 g/1,000 kcal, and 5
) moderate exercise for ≥30 min/day. During the first year of the study, body weight decreased on average 4.5 kg in the intervention group and 1.0 kg in the control group subjects (P
< 0.0001). Indicators of central adiposity and fasting glucose and insulin, 2-h postchallenge glucose and insulin, and A1C were all reduced significantly in the intervention group compared with the control group at 1-year examination ().
Figure 1 Changes in clinical and metabolic characteristics among the intervention and control group participants of the DPS. 2h-P-gluc, 2-h plasma glucose; DIAST, diastolic blood pressure; F-P-gluc, fasting plasma glucose; S, serum; SYST, systolic blood pressure. (more ...)
The U.S. Diabetes Prevention Program (DPP) (22
) recruited 3,234 individuals with IGT (and fasting plasma glucose ≥95 mg/dl) who were randomized to receive intensive dietary and exercise counseling, metformin, or placebo. The main aims of the intervention were ≥7% weight reduction and ≥150 min/week moderate physical activity. The relative risk reduction after 2.8 years was 58% in the lifestyle intervention group compared with the placebo group. The effect of lifestyle was higher than the effect of metformin, which showed 35% relative risk reduction. During the first year of the intervention, weight reduction was 5.6 kg (~6%), with slight, gradual regain to the end of the study at year 4 (23
The Indian Diabetes Prevention Program (14
) recruited 531 people with IGT who were randomized into four groups (control, lifestyle modification, metformin, and combined lifestyle modification and metformin). Lifestyle modification included advice on physical activity (30 min of brisk walking per day) and reduction in total calories, refined carbohydrates and fats, avoidance of sugar, and increase in fiber-rich foods. The intensity of the intervention was lower than in the DPP and DPS. After median follow-up of 30 months, the relative risk reduction in type 2 diabetes incidence was with lifestyle modification, 26.4% with metformin, and 28.2% with lifestyle modification and metformin, as compared with the control group. Thus, there was no added benefit from combining the pharmacologic and lifestyle interventions.
The Japanese trial (24
) included 458 IGT men randomized to receive either intensive lifestyle intervention (n
= 102) or standard intervention (n
= 356). The aims of the intensive intervention were body weight reduction if BMI was ≥22 kg/m2
(otherwise, to maintain present weight), to consume large amounts of vegetables while reducing the amount of other foods by 10%, reduction of fat (<50 g/day) and alcohol intake (<50 g/day), and physical activity >30–40 min/day. The cumulative 4-year incidence of type 2 diabetes in the intervention group was 67% lower than in the control group. Body weight decreased by 2.2 and 0.4 kg in the intervention and control groups, respectively.