Effects of higher-protein dietary interventions on lipid profile in adults with type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials

Dyslipidemia is a major cardiovascular risk factor in type 2 diabetes mellitus (T2DM). Higher-protein diets may improve cardiometabolic health, but their effects on lipid profile remain uncertain. This systematic review and meta-analysis evaluated the effects of higher-protein dietary interventions on lipid parameters in adults with T2DM. PubMed, Scopus, and Web of Science were searched through August 2026 for randomized controlled trials comparing higher-protein diets (≥ 20% of total energy from protein) with control diets in adults with T2DM. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were pooled using fixed- or random-effects models. Sensitivity, subgroup, meta-regression, and publication bias analyses were performed. Twenty randomized controlled trials involving 1,480 participants were included. Higher-protein diets significantly reduced triglycerides (WMD: − 0.17 mmol/L; 95% CI: − 0.29, − 0.06; P = 0.002) and total cholesterol (WMD: − 0.13 mmol/L; 95% CI: − 0.22, − 0.04; P = 0.003), while increasing HDL-cholesterol (WMD: 0.03 mmol/L; 95% CI: 0.01, 0.05; P = 0.003). No significant effect was observed for LDL-cholesterol (WMD: − 0.007 mmol/L; 95% CI: − 0.081, 0.067; P = 0.847). Sensitivity analyses confirmed the robustness of the findings. Meta-regression identified age as a significant modifier of triglyceride and total cholesterol responses, and no evidence of publication bias was detected. Higher-protein dietary interventions improve lipid profile in adults with T2DM by lowering triglycerides and total cholesterol and modestly increasing HDL-cholesterol without affecting LDL-cholesterol. These findings support higher-protein diets as an individualized nutritional strategy to improve cardiometabolic risk in T2DM and warrant confirmation in long-term randomized trials.