Reducing the Risk of Developing Diabetes
Welcome to the next installment of our CDE Exam Study Guide series. Now that we have covered how to identify individuals at risk in Chapter 4: Screening, we move to the crucial next step: Prevention.
Chapter 5, “Reducing the Risk of Developing Diabetes,” is a high-yield topic for the Canadian Certified Diabetes Educator (CDE) exam. As educators, we are often the first point of contact for patients diagnosed with prediabetes. Understanding the hierarchy of interventions—and specifically where pharmacotherapy fits in—is essential for both clinical practice and exam success.
Why this chapter matters for the CDE Exam:
The guidelines are very specific about the efficacy of lifestyle versus medication. A key “gold nugget” to remember is that intensive healthy behaviour interventions are the gold standard, capable of reducing the risk of type 2 diabetes by nearly 60%. In comparison, metformin reduces this risk by approximately 30%.
- The “5% Rule”: The target for weight loss in prediabetes is approximately 5% of initial body weight.
- The Candidates for Metformin: While lifestyle is for everyone, metformin is specifically considered for those with IGT, IFG, or an A1C of 6.0%–6.4%, particularly if they are younger (<60 years), have a BMI >35 kg/m², or have a history of gestational diabetes.
- Type 1 vs. Type 2: Remember that while we have actionable strategies for Type 2, prevention of Type 1 diabetes is currently restricted to formal research protocols only.
Below is a summarized study guide to help you navigate the evidence, the dietary patterns (Mediterranean, DASH, AHEI), and the clinical decision flow.
1. Chapter Overview
This chapter focuses on interventions to prevent or delay the onset of type 2 diabetes in high-risk individuals and the current status of prevention strategies for type 1 diabetes. For the CDE exam, focus heavily on the hierarchy of interventions (Lifestyle > Metformin) and the specific dietary patterns recommended.
2. Key Messages (The "Gold Nuggets")
- Type 1 Diabetes: As safe and effective preventive therapies have not yet been identified, prevention attempts should be undertaken only within the confines of formal research protocols.
- Lifestyle Efficacy: Intensive healthy behaviour interventions, ideally resulting in a loss of ~5% of initial body weight, can reduce the risk of type 2 diabetes by almost 60%.
- Durability: When initiated early, the effects of healthy behaviour interventions are long-lasting (more than 20 years).
- Pharmacotherapy: Metformin reduces the risk of progression to type 2 diabetes by approximately 30%, with persistent benefits observed after stopping treatment.
- Role of Dietitians: A registered dietitian can educate patients about dietary changes to reduce diabetes risk.
3. Prevention of Type 1 Diabetes
- Current Status: Interventions such as nicotinamide (ENDIT trial), insulin injections (DPT-1), and elimination of cow’s milk protein (TRIGR) have not shown success in preventing Type 1 diabetes in general populations.
- Clinical Rule: Attempts to prevent type 1 diabetes should be restricted to formal research protocols.
4. Prevention of Type 2 Diabetes: Interventions
A. Healthy Behaviour Interventions (First Line)
- Target: Weight loss of approximately 5% of initial body weight.
- Physical Activity: Moderate-intensity activity of at least 150 minutes per week.
- Evidence:
- DPP & DPS Trials: Showed a 58% risk reduction at 4 years.
- Da Qing Study: 23-year follow-up showed reduced all-cause and cardiovascular mortality.
B. Dietary Patterns
There is strong evidence to support specific dietary patterns.
- Mediterranean Diet:
- High adherence reduces the risk of future diabetes by 19% to 23%.
- Supplementation with Extra Virgin Olive Oil (EVOO) or mixed nuts reduced diabetes risk by 40% and 18% respectively in the PREDIMED trial.
- DASH Diet: (Dietary Approaches to Stop Hypertension) is consistently associated with a reduced risk of type 2 diabetes.
- AHEI: (Alternate Healthy Eating Index) is consistently associated with a reduced risk of type 2 diabetes.
- Specific Foods:
- Whole Grains: Consuming more than 2 servings per day is associated with a 43% reduced risk.
- Dairy: An inverse association (more dairy = less diabetes) exists for total dairy up to 300–400 g/day.
- Sugar-Sweetened Beverages: Higher intake is associated with higher risk, independent of body weight.
C. Pharmacotherapy
- Metformin:
- Efficacy: Decreased progression to diabetes by 31% compared to placebo.
- Best Candidates: Metformin may be considered for people with Impaired Glucose Tolerance (IGT), especially if they also have Impaired Fasting Glucose (IFG) or an A1C of 6.0%–6.4%. It is most effective in younger individuals (<60 years), those with significant obesity (BMI >35 kg/m²), and women with a history of Gestational Diabetes (GDM).
- Other Agents (Not First Line/Specific Contexts):
- Thiazolidinediones (TZDs): Rosiglitazone and Pioglitazone reduce risk significantly (60-72%) but are not recommended for widespread use due to adverse effects like weight gain and edema.
- Acarbose: Reduced risk by 25%, but the effect did not persist after discontinuation.
- Liraglutide: Shown to prevent conversion to diabetes and induce weight loss, but cost and long-term safety remain considerations.
- Orlistat: Reduced incidence by 37% but had a high dropout rate due to side effects.
- Vitamin D: Has no significant effects on insulin resistance or prevention in trials to date.
D. Bariatric Surgery
- Shows a drastic risk reduction (Odds Ratio 0.10).
- Limitations: The cost-benefit analysis for primary prevention is unclear, so it is not routinely recommended solely for prevention.
5. Clinical Decision Algorithm
For the exam, visualize the flow of treatment for a patient with Prediabetes:
- START: Diagnose Prediabetes.
- INTERVENTION:
- Healthy Behaviour Interventions (Goal: ≥5% weight loss).
- AND/OR Dietary Patterns (Mediterranean, DASH, AHEI).
- Consider Metformin in addition to lifestyle (esp. if high risk).
- MONITOR: Check A1C/FPG in 3 to 6 months.
- DECISION:
- Stable/Improved? -> Maintain current strategy, follow up every 6 months.
- Not Improved? -> Intensify healthy behaviour, consider adding/increasing Metformin.
6. 2018 Clinical Practice Guidelines Recommendations
These are the “Must Memorize” graded recommendations for the exam.
- Healthy Behaviour: In individuals with prediabetes, a structured program of healthy behaviour interventions that includes moderate weight loss and regular physical activity of a minimum of 150 minutes per week should be implemented to reduce the risk of type 2 diabetes.
- Dietary Patterns: In individuals at risk for type 2 diabetes, dietary patterns may be used to reduce the risk of diabetes, specifically:
- Mediterranean-style.
- DASH (Dietary Approaches to Stop Hypertension).
- AHEI (Alternate Healthy Eating Index).
- Metformin: In individuals with prediabetes, pharmacologic therapy with metformin may be used to reduce the risk of type 2 diabetes.