Effect of partial replacement of animal protein with plant protein on glycemic control in type 2 diabetes: Rationale, design, and protocol of a randomized clinical trial.

BACKGROUND AND AIMS: The management of type 2 diabetes mellitus (T2DM) includes pharmacological therapy, lifestyle modification, and dietary interventions, among which plant-based diets have been shown to improve glycemic control and cardiometabolic health. However, few studies have evaluated plant-based approaches that allow modest meat intake while altering the proportion of animal- and plant-derived protein. We are conducting a randomized clinical trial to assess whether a plant-based dietary pattern with partial substitution of animal protein improves glycemic control in adults with T2DM and overweight/obesity.

METHODS AND RESULTS: Participants are randomized to either a plant-based diet or a standard healthy diet aligned with international T2DM guidelines, and both groups receive individualized energy prescriptions targeting a 5% weight loss over 24 weeks. The interventions differ primarily in protein-source distribution: the control diet provides 15% of total energy from animal protein and 5% from plant protein, whereas the plant-based diet provides 15% from plant protein and 5% from animal protein. Diets are adapted to Brazilian eating habits and local food availability. A total of 146 participants will be enrolled (73 per group). The primary outcome is the between-group difference in glycated hemoglobin (HbA1c) at 24 weeks. Key secondary outcomes include glycemic variability, body weight and composition, lipid profile, and inflammatory biomarkers. Participants undergo anthropometric, laboratory, and psychometric assessments.

CONCLUSION: This trial addresses evidence gaps regarding the metabolic effects of flexible, culturally adapted plant-based diets in T2DM. This manuscript describes the rationale and protocol of the ongoing trial.

TRIAL REGISTRATION: NCT05706155.