Low-Carbohydrate and Ketogenic Dietary Patterns for Type 2 Diabetes Management

The prevalence of diabetes continues to increase despite advances in treatment options. In 2019, according to the Centers for Disease Control and Prevention (CDC), 37.1 million (14.7%) US adults had diabetes. Among adults aged ≥ 65 years, the prevalence is even higher at 29.2%.¹ Research has also estimated that 45% of adults have evidence of prediabetes or diabetes.² According to the Veterans Health Administration, almost 25% of enrolled veterans have diabetes.³

Background

Diabetes is associated with an increased risk of microvascular complications (eg, retinopathy, nephropathy, and neuropathy) and macrovascular complications (eg, atherosclerotic cardiovascular disease) and is one of the most common causes of morbidity and mortality in the US.⁴ In 2017, diabetes was estimated to cost $327 billion in the US, up from $261 billion in 2012.⁵ During this same period, the excess costs per person with diabetes increased from $8417 to $9601.⁵

Type 2 diabetes mellitus (T2DM) and its associated insulin resistance is typically considered a chronic disease with progressive loss of β-cell function. Controlling glycemia, delaying microvascular changes, and preventing macrovascular disease are major management goals. Lifestyle interventions are essential in the management and prevention of T2DM. Medication management for T2DM usually progresses through several medications, ending in insulin therapy.⁶ Within 10 years of diagnosis, almost half of all individuals with T2DM will require insulin to manage their glycemia.⁷

Bariatric surgery and nutrition approaches have been successful in reversing T2DM. Recently, there has been increased interest in nutritional approaches to place T2DM in remission, reverse the disease process, and improve insulin resistance. Contrary to popular belief, before the discovery of insulin in 1921, low-carbohydrate (LC) diets were the most common treatment for T2DM.⁸ With the discovery of insulin and the eventual development of low-fat dietary recommendations, LC diets were no longer favored by most clinicians.⁸ Low-fat diets are, by definition, also high-carbohydrate diets. By the early 1980s, low-fat diets had become the standard of care dietary recommendation, and the goal for clinicians became glycemic maintenance (with increased use of medications) rather than preventing hyperglycemia.⁸

With growing evidence regarding the use of LC diets for T2DM, the US Department of Veterans Affairs (VA) and US Department of Defense (DoD), the American Diabetes Association (ADA), the European Association for the Study of Diabetes (EASD), Diabetes Canada, and Diabetes Australia all include LC diets as a viable option for treating T2DM.^4,9-12 This article will highlight a case using a reduced carbohydrate approach in lifestyle management and provide clinicians with practical guidance in its implementation. We will review the evidence that informs these guidelines, describe a practical approach to nutritional counseling, and review medication management and deprescribing approaches. Finally, barriers to implementation will be explored.

ILLUSTRATIVE CASE

A 64-year-old woman presented to the clinical pharmacist for the management of T2DM after her tenth hospitalization related to hyperglycemia in 10 years. She had previously been managed by primary care clinicians, clinical dietitians, endocrinologists, and certified diabetes care and education specialists. Pertinent history included diabetic ketoacidosis, coronary artery disease, hyperlipidemia, hypertension, obstructive sleep apnea, obesity, metabolic dysfunction-associated steatotic liver disease, and mild nonproliferative diabetic retinopathy with clinically significant macular edema. The patient expressed frustration with poor glycemic control during her many years of insulin therapy and an inability to lose weight due to insulin dose titrations. The patient reported prior education including but not limited to standardized sample menus, consistent carbohydrate intake, calorie reduction, general healthful nutrition, and the “move more, eat less” approach. The patient was unable to titrate insulin dosage and did not experience weight loss despite compliance with these methods.

Her medications included glargine insulin 45 units once daily, aspart insulin 5 units before meals 3 times daily, and metformin 1000 mg twice daily. Her hemoglobin A_1c (HbA_1c) level was 11.8%. A review of prior therapies for T2DM included glyburide 5 mg twice daily, metformin 1000 mg twice daily, 70/30 insulin (up to 340 units/d), glargine insulin (range, 10-140 units/d), regular insulin (range, 30-240 units/d), aspart insulin (range, 15-45 units/d), and U-500 regular insulin (range, 125-390 units/d). She took metoprolol 25 mg extended release daily and hydrochlorothiazide 25 mg daily, but both were discontinued after the most recent hospitalization. A review of HbA_1c readings showed poor glycemic control for > 12 years (range, 10.3% to > 12.3%).

Education for lifestyle modifications, including an LC diet, was presented to the patient to assist with weight loss, improve glycemic control, and reduce insulin resistance. In addition, a glucagon-like peptide-1 agonist (liraglutide) was added to her pharmacotherapy. Continued dietary modifications with LC intake led to consistent reductions in glargine and aspart insulin therapy. The patient remained motivated throughout clinic visits due to improved glycemic control with sustainable dietary modifications, consistently reported feeling better overall, and deprescribed diabetes drug therapies. She remained off her blood pressure medications. After4 months of LC dietary modifications, all insulin therapy was discontinued. She continued with liraglutide 1.8 mg daily and metformin 1000 mg twice daily with an HbA_1c of 6.3%. Two months later, her HbA_1c level was 6.0%. She also lost 8 lb and her body mass index improved from 31 to 29.