Comparing the Effectiveness of Different Dietary Educational Approaches for Carbohydrate Counting on Glycemic Control in Adults with Type 1 Diabetes: Findings from the DIET-CARB Study, a Randomized Controlled Trial.

Background/objectives: Carbohydrate counting is recommended to improve glycemic control in type 1 diabetes (T1D), but the most effective educational methods are unclear. Despite its benefits, many individuals struggle with mastering carbohydrate counting, leading to inconsistent use and suboptimal glycemic outcomes. This study aimed to compare the effectiveness of two group-based programs with individual dietary counseling (standard care) for glycemic control.

Methods: The trial was a randomized, controlled, open-label, parallel-group design. Adults with T1D on multiple daily insulin injections (MDIs) and with glycated hemoglobin A1c (HbA1c) 53-97 mmol/mol were randomly assigned (1:1:1) to basic (BCC), advanced carbohydrate counting (ACC), or standard care. Primary outcomes were the changes in HbA1c or mean amplitude of glycemic excursions (MAGEs) in BCC and ACC versus standard care after six months. Equivalence testing was performed to compare BCC and ACC.

Results: Between November 2018 and August 2021, 63 participants were randomly assigned to BCC (N = 20), ACC (N = 21), or standard care (N = 22). After 6 months, HbA1c changed by -2 mmol/mol (95% CI -5 to 0 [-0.2%, -0.5 to 0]) in BCC, -4 mmol/mol (-6 to -1 [-0.4%, -0.6 to -0.1]) in ACC, and -3 mmol/mol (-6 to 0 [-0.3%, -0.6 to 0]) in standard care. The estimated difference in HbA1c compared to standard care was 1 mmol/mol (-3 to 5 [0.1%, -0.3 to 0.5]); = 0.663 for BCC and -1 mmol/mol (-4 to 3 [-0.1%, -0.4 to 0.3]); = 0.779 for ACC. For MAGEs, changes were -0.3 mmol/L (-1.5 to 0.8) in BCC, -0.0 mmol/L (-1.2 to 1.1) in ACC, and -0.7 mmol/L (-1.8 to 0.4) in standard care, with differences of 0.4 mmol/L (-1.1 to 1.9); = 0.590 for BCC and 0.7 mmol/L (-0.8 to 2.1); = 0.360 for ACC versus standard care. An equivalence in effect between BCC and ACC was found for HbA1c, but not for MAGEs.

Conclusions: Group-based education in BCC and ACC did not demonstrate a clear advantage over individualized dietary counseling for overall glycemic control in adults with T1D. Healthcare providers should consider flexible, patient-centered strategies that allow individuals to choose the format that best suits their learning preferences when selecting the most suitable dietary educational approach.