Effect of dietary carbohydrate intake on glycaemic control and insulin resistance in type 2 diabetes: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES: The aim of this study was to elucidate the dose-response relationship between dietary carbohydrate consumption and the improvement of glycemic control and insulin sensitivity in indi-viduals with type 2 diabetes mellitus (T2DM), following an intensive dietary intervention. METHODS AND STUDY DESIGN: Randomized controlled trials published up to December 2023 were systematically reviewed from four databases: PubMed, Embase, Web of Science, and Cochrane Database of Systematic Reviews. Primary outcomes included: glycated hemoglobin (HbA1c), fasting glucose (FG); and secondary outcomes included: BMI, fasting insulin (FI), Homeostasis Model Assessment-Insulin Resistance (HOMA-IR). We performed a random-effects dose-response meta-analysis to estimate mean differences (MDs) for each 10% reduction in carbohydrate intake. RESULTS: A total of 38 articles were analyzed, encompassing 2,831 total par-ticipants. Compared to the highest recorded carbohydrate intake (65%), reducing carbohydrate intake to 5% showed that for every 10% decrease, the following improvements were observed: HbA1c (MD: 0.39%; 95%CI: -0.5 to -0.28%), FG (MD: 0.55 mmol/L; 95%CI: -0.82 to -0.28 mmol/L), BMI (MD: -0.83 kg/m2; 95%CI: -1.27 to -0.38 kg/m2), FI (MD: -2.19 pmol/L; 95%CI: -3.64 to -0.73 pmol/L), HOMA-IR (MD: -1.53; 95%CI: -3.09 to 0.03). CONCLUSIONS: Reducing dietary carbohydrate intake significantly improves glycemic control and insulin resistance in individuals with type 2 diabetes. A linear reduction in carbohydrate intake was observed, with significant effects occurring within the first 6 months of the intervention. However, these effects diminished beyond this period. Notably, the improvements in glycemic parameters were not significantly affected by whether calorie restriction was implemented.