Effect of Low-Carbohydrate Diets on Glycemic Control in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Low-carbohydrate diets have gained increasing attention as a strategy for improving glycemic control in individuals with type 2 diabetes mellitus (T2DM). However, evidence from randomized controlled trials (RCTs) remains variable. This study aimed to evaluate the effect of low-carbohydrate diets on HbA1c levels in patients with T2DM through a systematic review and meta-analysis of RCTs. A systematic search was conducted to identify RCTs comparing low-carbohydrate diets with control diets in adults with T2DM, including studies with mixed populations where applicable. The primary outcome was change in HbA1c. Data were pooled using a random-effects model, and heterogeneity was assessed using the I² statistic. Sensitivity analysis and funnel plot assessment were performed. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool. Seven RCTs comprising 562 participants were included. Low-carbohydrate diets were associated with a statistically significant reduction in HbA1c compared with control diets (mean difference: -0.24%; 95% CI: -0.32 to -0.16; p<0.00001). Heterogeneity was low (I²=6%). Sensitivity analysis demonstrated consistent results with no single study significantly influencing the overall estimate. Funnel plot assessment showed no clear evidence of publication bias, although interpretation was limited by the small number of studies. Low-carbohydrate diets are associated with a modest but statistically significant and clinically relevant improvement in glycemic control in patients with T2DM. These findings support their role as a dietary strategy in diabetes management.