The Role of Different Dietary Models in Medical Nutrition Therapy for Type 1 and Type 2 Diabetes: From Past to Present

Abstract

Medical nutrition therapy (MNT) is a fundamental component that complements pharmacological treatment in the management of both type 1 and type 2 diabetes. However, current evidence indicates that there is no single ideal diet suitable for everyone and that the nutritional approach should be individualized. In this review, the role of different dietary models in the medical nutrition therapy of type 1 and type 2 diabetes management is evaluated-on the basis of current guidelines and meta-analyses predominantly from the 2020–2026 period-in terms of their definitions and mechanisms of action, glycemic and cardiometabolic evidence bases, applicability in the two types of diabetes, sustainability dimensions, and safety and adherence. The models addressed include the Mediterranean diet, DASH, low- and very-low-carbohydrate (ketogenic) diets, the low glycemic index/load approach, plant-based (vegetarian, vegan, and Portfolio) diets, high-protein/moderate-carbohydrate approaches, intermittent fasting and time-restricted eating, and very-low-energy diets targeting type 2 diabetes remission. Current evidence shows that multiple dietary patterns significantly improve glycemic control, that this benefit is largely mediated by weight loss, and that the decisive factor in long-term success is the sustainability of adherence rather than the type of model. In type 2 diabetes, energy balance, weight loss, and-in suitable individuals-remission are prominent, whereas in type 1 diabetes, carbohydrate counting and insulin-dose matching are of primary importance. Furthermore, it is notable that the dietary patterns strongly recommended for health (the Mediterranean, low glycemic index, and plant-based diets) overlap with the most environmentally sustainable models. In conclusion, in the management of diabetes, evidence-based dietary models should be individualized and sustained with long-term professional support.