Dietary patterns and type 2 diabetes: A narrative review

The global prevalence of type 2 diabetes (T2D) continues to rise, posing a significant public health challenge worldwide. In recent years, modifications to dietary patterns have emerged as a promising strategy for the prevention and management of T2D. Evidence suggests that different dietary patterns exert varying effects on key metabolic indicators such as blood glucose, glycated hemoglobin (HbA1c), and insulin sensitivity. This narrative review summarizes current findings on the associations between several major dietary patterns—including vegetarian, omnivorous, low-carbohydrate, Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and Western diets—and T2D-related outcomes, while also identifying limitations in the existing literature. Healthy dietary patterns, particularly vegetarian, low-carbohydrate, Mediterranean, and DASH diets, have been shown to effectively reduce HbA1c levels, enhance insulin sensitivity, and support weight management. In contrast, excessive consumption of Western diets and ultra-processed foods is consistently linked to a heightened risk of T2D. However, inconsistencies in study design, population characteristics, and definitions of dietary patterns hinder direct comparisons across studies. To advance the field, future research should prioritize long-term, standardized, and cross-national randomised controlled trials to elucidate the distinct nutritional and biological mechanisms underlying each dietary approach. These efforts are crucial for developing practical, evidence-based dietary guidelines aimed at reducing the global burden of T2D.