# Structural Concepts, Definition, Classification, and Macronutrient and Food Composition of Carbohydrate-Restricted Diets for Individuals with Type 2 Diabetes Mellitus: A Scoping Review

## TL;DR

This review examines the structure and composition of low-carb diets for people with type 2 diabetes, highlighting inconsistencies in definitions and food details.

## Contribution

The study systematically reviews and clarifies the structural concepts and variability in carbohydrate-restricted diets for T2DM.

## Key findings

- CRDs reduce insulin needs and support glycemic control in T2DM patients.
- Definitions and food composition details of CRDs are inconsistent across studies.
- Diverse guidelines for CRDs hinder comparison and adherence to dietary recommendations.

## Abstract

Objective: This study aimed to review the structural concepts, definition, classification, and macronutrient and food composition of carbohydrate-restricted diets (CRDs) for individuals with type 2 diabetes mellitus (T2DM). Methods: A scoping review was conducted following Joanna Briggs Institute guidelines. Searches were performed in Scopus, PubMed, Web of Science, and Embase, including texts published in Portuguese, English, and Spanish. Official documents from governments, regulatory agencies, and international diabetes organizations were also consulted. Results: In total, 79 articles and 17 official documents were analyzed. The following structural concept was identified: restricted carbohydrate intake decreases the need for endogenous and exogenous insulin, contributing to the maintenance of glycemic control, and justifies its consideration among the nutritional therapy options for individuals with T2DM. CRDs varied in definition, classification, and macronutrient composition. Studies failed to provide detailed information on the food composition of diets, precluding an in-depth understanding of metabolic effects. The existence of several approaches with varying recommendations makes it difficult to generalize the results. International CRD guidelines for T2DM adopt divergent definitions, compromising interpretation, recommendation, and even adherence. Conclusions: Although the concept of CRDs justifies their adoption within the nutritional therapy choices for T2DM, the multiple denominations can hinder understanding and comparison between studies. The lack of information on food composition and carbohydrate types compromises the assessment of the effects and adherence to CRD-based nutritional interventions. We emphasize the need for methodologically consistent studies that evaluate CRDs based on fresh and minimally processed foods with a low glycemic index to support official diabetes guidelines and organizations.