Low-Carbohydrate and Ketogenic Dietary Patterns for Type 2 Diabetes Management
Background: Type 2 diabetes mellitus (T2DM) has been traditionally considered a chronic, progressive disease. Since 2017, guidelines from the US Department of Veterans Affairs and US Department of Defense have included low-carbohydrate (LC) dietary patterns in managing T2DM. Recently, carbohydrate reduction, including ketogenic diets, has gained renewed interest in the management and remission of T2DM.
Observations: This narrative review examines the evidence behind carbohydrate reduction in T2DM and a practical guide for clinicians starting patients on therapeutic LC diets. We present an illustrative case and provide practical approaches to prescribing a very LC ketogenic (< 50 g), LC (50-100 g), or a moderate LC (101-150 g) dietary plan and discuss adverse effects and management of LC diets. We provide a medication management and deprescription approach and discuss strategies to consider in conjunction with LC diets. As patients adopt LC diets, glycemia improves, and medications are deprescribed, hemoglobin A1c levels and fasting glucose may drop below the diagnostic threshold for T2DM. Remission of T2DM may occur with LC diets (hemoglobin A1c < 6.5% for ≥ 3 months without T2DM medications). Finally, we describe barriers and limitations to applying therapeutic carbohydrate reduction in a federal health care system.
Conclusions: The effective use of LC diets with close and intensive lifestyle counseling and a safe approach to medication management and deprescribing can improve glycemic control, reduce the overall need for insulin and medication and provide sustained weight loss. The efficacy and continuation of therapeutic carbohydrate reduction for patients with T2DM appears promising. Further research on LC diets, emerging strategies, and long-term effects on cardiometabolic risk factors, morbidity, and mortality will continue to inform practice.
Starting an LC dietary pattern should maximize nutrient-dense and minimally processed proteins. Clinicians should begin with a baseline nutritional assessment through a 24-hour recall or food diary. After this has been completed, the patient’s baseline diet is assessed, and a gradual carbohydrate reduction plan is discussed. Generally, carbohydrate reduction is recommended at 1 meal per day per week. High-carbohydrate meals and snacks are restructured to favor satiating, minimally processed, high-protein food sources. Individual food preferences are considered and included in the recommended LC plan. For example, LC diets can be formulated for vegetarians and vegans as well as those who prefer meat and seafood. Prioritizing satiating and nutrient-dense foods can help increase the probability of diet acceptance and adherence.
A recent study showed that restricting carbohydrates at breakfast reduces 24-hour postprandial hyperglycemia and improves glycemic variability.26 Many patients consume upward of 50 g of carbohydrates at breakfast.27 For example, it is not uncommon for a patient to consume cereal with milk or oatmeal, orange juice, a banana, and toast at breakfast. Instead, the patient is advised to consume any combination of eggs, meat, no-sugar-added Greek yogurt, or berries.
To keep things simple for lunch and dinner, the patient is offered high-quality, minimally processed protein of their choosing with any nonstarchy vegetable. Should a patient desire additional carbohydrates with meals, they may reduce the baseline serving of carbohydrates by 50%. For example, if a patient normally fills 50% of their plate with spaghetti, they may reduce the pasta portion to 25% and add a meatball or increase the amount of vegetables consumed with the meal to satiety.
Snacks may include cheese, eggs, peanut butter, nuts, seeds, berries, no-sugar-added Greek yogurt, or guacamole. Oftentimes, when LC meals are adopted, the desire or need for snacking is diminished due to the satiating effect of high-quality protein sources and nonstarchy vegetables.
Adverse Effects
AEs have been reported with VLCK diets, including headache, diarrhea, constipation, muscle cramps, halitosis, light-headedness, and muscle weakness.28 These AEs may be mitigated with increased fluid intake, sodium intake, and magnesium supplementation.29 Increasing fluids to a minimum of 2 L/d and adding sodium (eg, bouillon supplementation) can minimize AEs.30 Milk of magnesia (5 mL) or slow-release magnesium chloride 200 mEq/d is suggested to reduce muscle cramps.30 There have been no studies looking at sodium intake and worsening hypertension or chronic heart failure in the setting of an LC diet, but fluid and electrolyte intake should be monitored closely, especially in patients with uncontrolled hypertension and heart failure. Other concerns of higher protein on worsening kidney function have generally not been founded.31 In some individuals, an LC and higher fat diet may increase low-density lipoprotein cholesterol (LDL-C).32 Therefore a baseline lipid panel is recommended and should be monitored along with HbA1c levels. An elevated LDL-C response may be managed by increasing protein and reducing saturated fat intake while maintaining the reduced carbohydrate content of the diet.
Medication Management
The adoption of an LC diet can cause a swift and profound reduction in blood sugar.33 Utilizing PACTs can help prevent adverse drug events by involving clinical pharmacists to provide recommendations and dose reductions as patients adopt an LC diet. Each approach must be individualized to the patient and can depend on several factors, including the number and strength of medications, the degree of carbohydrate reduction, baseline blood glucose, as well as assessing for medical literacy and ability to implement recommendations. Additionally, patients should monitor their blood sugar regularly and communicate with their primary care team (pharmacist, PACT registered nurse, primary care clinician, and registered dietician). Ultimately, the goal when adopting an LC diet while taking antihyperglycemics is safely avoiding hypoglycemia while reducing the number of medications the patient is taking. We summarize a practical approach to medication management that was recently published (Table 3).33,34
