4. Prevention or Delay of Type 2 Diabetes
Patients with prediabetes should be referred to an intensive diet and physical activity behavioral counseling program adhering to the tenets of the Diabetes Prevention Program (DPP) targeting a loss of 7% of body weight and should increase their moderate-intensity physical activity (such as brisk walking) to at least 150 min/week. A
Follow-up counseling and maintenance programs should be offered for long-term success in preventing diabetes. B
Based on the cost-effectiveness of diabetes prevention, such programs should be covered by third-party payers. B
Metformin therapy for prevention of type 2 diabetes should be considered in those with prediabetes, especially in those with BMI >35 kg/m2, those aged <60 years, and women with prior gestational diabetes mellitus. A
At least annual monitoring for the development of diabetes in those with prediabetes is suggested. E
Screening for and treatment of modifiable risk factors for cardiovascular disease is suggested. B
Diabetes self-management education and support programs are appropriate venues for people with prediabetes to receive education and support to develop and maintain behaviors that can prevent or delay the onset of diabetes. B
Technology-assisted tools including Internet-based social networks, distance learning, DVD-based content, and mobile applications can be useful elements of effective lifestyle modification to prevent diabetes. B
Randomized controlled trials have shown that individuals at high risk for developing type 2 diabetes (impaired fasting glucose, impaired glucose tolerance, or both) can significantly decrease the rate of diabetes onset with particular interventions (1–7). These include intensive lifestyle modification programs that have been shown to be very effective (∼58% reduction after 3 years). Follow-up of all three large studies of lifestyle intervention has shown sustained reduction in the rate of conversion to type 2 diabetes: 43% reduction at 20 years in the Da Qing study (8), 43% reduction at 7 years in the Finnish Diabetes Prevention Study (DPS) (9), and 34% reduction at 10 years in the U.S. Diabetes Prevention Program Outcomes Study (DPPOS) (10).
A cost-effectiveness model suggested that lifestyle interventions in the Diabetes Prevention Program (DPP) are cost-effective (11). Actual cost data from the DPP and DPPOS also confirm this (12). Group delivery of DPP content into community settings has the potential to reduce overall program costs while still producing weight loss and diabetes risk reduction (13,14). The Centers for Disease Control and Prevention (CDC) helps to coordinate the National Diabetes Prevention Program, a resource designed to bring evidence-based lifestyle change programs for preventing type 2 diabetes to communities (http://www.cdc.gov/diabetes/prevention/index.htm).
Given the clinical trial results and the known risks of progression from prediabetes to diabetes, people with an A1C 5.7–6.4% (39–46 mmol/mol), impaired glucose tolerance, or impaired fasting glucose should be counseled on lifestyle changes with goals similar to those of the DPP (7% weight loss and moderate-intensity physical activity of at least 150 min/week).
As for people with diabetes (see Section 3 “Foundations of Care and Comprehensive Medical Evaluation”), evidence supports the importance of maintaining a healthy diet in order to prevent diabetes onset. Unlike past recommendations that focused on simply reducing total dietary fat and cholesterol consumption, more recent evidence argues against the preventative effects of lowering fat and cholesterol intake across the board and supports instead that the quality of fats consumed in the diet is more important than the total quantity of dietary fat. For example, recent work supports the Mediterranean diet, which is relatively rich in monounsaturated fats, as a means to help to prevent type 2 diabetes (15). Studies evaluating glycemic index to guide carbohydrate recommendations have been inconsistent (16,17); however, data suggest that consumption of a diet enriched in whole grains is helpful in preventing type 2 diabetes (18). Finally, increased consumption of nuts (19) and berries (20) in the context of a diet high in vegetables and whole fruits has been correlated with reduced diabetes risk. Individualized medical nutrition therapy (see Section 3 “Foundations of Care and Comprehensive Medical Evaluation” for more detailed information) has been shown to be effective in lowering A1C in individuals diagnosed with prediabetes (7). This indicates that nutritional interventions are potentially effective in staving off the progression toward type 2 diabetes (e.g., individuals showing signs of metabolic syndrome).
Physical Activity and Exercise
Physical activity and exercise are important for those living with diabetes (see Section 3 “Foundations of Care and Comprehensive Medical Evaluation”), but they have also been evaluated for diabetes prevention. Physical activity is a more general term that covers all types of activity, whereas exercise refers to structured or planned activities. Although not well studied in isolation, exercise and physical activity have been validated to prevent or delay diabetes development as part of a comprehensive approach to lifestyle modification (21). These studies suggest that while exercise treatment programs may not reduce body weight, programs of sufficient intensity have been shown to decrease diabetes risk (21). Therefore, health care providers should inform at-risk patients of these benefits in order to motivate them to engage in regular moderate-intensity physical activity.
Moderate exercise, such as brisk walking or other activities of equivalent intensity, has been also observed to improve insulin sensitivity and reduce abdominal fat content in children and young adults (22,23). The DPP included 150 min/week of moderate-intensity exercise and showed beneficial effect on glycemia in those with prediabetes (1). Both resistance training and endurance exercise appear to have beneficial effects on waist circumference, insulin sensitivity, and thus diabetes risk (24,25). The preventative effects of exercise appear to extend to the prevention of gestational diabetes mellitus (GDM) as well (26).
Prevention of Cardiovascular Disease
People with prediabetes often have other cardiovascular risk factors, such as obesity, hypertension, and dyslipidemia and are at increased risk for cardiovascular disease events. While treatment goals for people with prediabetes are the same as for the general population, increased vigilance is warranted to identify and treat these and other risk factors (e.g., smoking).
Technology Assistance to Deliver Lifestyle Modification
Technology may be an effective means to deliver the core components of the DPP (27,28). Initial studies have validated DVD-based content delivery (29). This has been corroborated in a primary care patient population (30). Recent studies support content delivery through virtual small groups (31), Internet-driven social networks (32,33), cellular phones, and other mobile devices. Mobile applications for weight loss and diabetes prevention have been validated for their ability to reduce A1C in the setting of prediabetes (33). The CDC’s Diabetes Prevention Recognition Program (DPRP) (http://www.cdc.gov/diabetes/prevention/recognition/index.htm) has begun to certify electronic and mobile health-based modalities as effective vehicles for DPP-style prevention content that may be considered alongside more traditional face-to-face and coach-driven programs.
Pharmacological agents, such as metformin, α-glucosidase inhibitors, orlistat, and thiazolidinediones, have each been shown to decrease incident diabetes to various degrees. Metformin has the strongest evidence base and demonstrated long-term safety as pharmacological therapy for diabetes prevention (34). For other drugs, cost, side effects, and durable efficacy require consideration.
Metformin was less effective than lifestyle modification in the DPP and DPPOS but may be cost-saving over a 10-year period (12). It was as effective as lifestyle modification in participants with BMI ≥35 kg/m2 but not significantly better than placebo in those over 60 years of age (1). In the DPP, for women with a history of GDM, metformin and intensive lifestyle modification led to an equivalent 50% reduction in diabetes risk (35), and both interventions remained highly effective during a 10-year follow-up period (36). Metformin may be recommended for high-risk individuals (e.g., those with a history of GDM, those who are very obese, and/or those with more severe or progressive hyperglycemia) and/or those with rising A1C despite lifestyle intervention.
Diabetes Self-Management Education and Support
As for those with established diabetes, the standards for diabetes self-management education and support (see Section 3 “Foundations of Care and Comprehensive Medical Evaluation”) can also apply to the education and support of people with prediabetes. Currently, there are significant barriers to the provision of education and support to those with prediabetes. However, the strategies for supporting successful behavior change and the healthy behaviors recommended for people with prediabetes are comparable to those for diabetes. Although reimbursement remains a barrier, studies show that providers of diabetes self-management education and support are particularly well equipped to assist people with prediabetes in developing and maintaining behaviors that can prevent or delay the onset of diabetes (7,37).
Suggested citation: American Diabetes Association. Prevention or delay of type 2 diabetes. Sec. 4. In Standards of Medical Care in Diabetes—2016. Diabetes Care 2016;39(Suppl. 1):S36–S38
- © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.