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Contrasting Ketogenic and Mediterranean Diets in Individuals With Type 2 Diabetes and Prediabetes

Study Aim

There is no consensus on the optimal dietary pattern for people with prediabetes and type 2 diabetes, especially between different low-carbohydrate diets. This study compared 2 low-carbohydrate diets: a well-formulated Ketogenic diet (WFKD) and a Mediterranean-plus Diet (Med-Plus), with 3 key similarities (incorporating non-starchy vegetables and avoiding added sugars and refined grains) and 3 key differences (incorporating compared with avoiding legumes, fruits, and whole, intact grains) for their effects on blood sugar control and cardiovascular risk factors in people with prediabetes and type 2 diabetes.

Eligible Participants

  • Adults, 18 years of age or older
  • Diagnosed with type 2 diabetes, OR prediabetes (defined as glycated hemoglobin (HbA1c) equal to of higher than 5.7% or fasting glucose greater than 100 mg/dL

Study Design

Forty participants followed the WFKD and the Med-Plus diet for 12 weeks each, in random order. The Med-Plus incorporated legumes, fruits, and whole, intact grains, while the WFKD avoided them. Participants attended up to 14 classes with a registered dietitian to achieve the best adherence to their prescribed diet, and completed dietary food records throughout the study to determine their energy and nutrient intake. They completed 7 clinic visits and provided blood and stool samples to assess body weight, HbA1c, fasting insulin, blood sugar, and blood lipids. They also wore a continuous glucose monitor for 2 weeks 6 times during the study to measure their average glucose.

Conclusions

The results of this study showed an improvement in HbA1c on both the WFKD and the Med-Plus diet, with no significant difference between the two diets. Both diets also led to a similar weight loss (7-8%). The WFKD led to a greater decrease in triglycerides, but also to elevated LDL cholesterol and lower nutrient intakes and fiber from avoiding legumes, fruits, and whole, intact grains. Finally, study participants deemed the WFKD less sustainable over time.

Research