Impact of bariatric surgery on glycaemic and metabolic outcomes in people with obesity and type 2 diabetes mellitus: A meta-analysis.

Aims: Bariatric surgery is a widely adopted intervention for managing obesity and improving glycaemic control in patients with type 2 diabetes mellitus (T2DM). This meta-analysis evaluates the impact of bariatric surgery on glycaemic and metabolic outcomes, including fasting blood glucose (FBG), postprandial glucose (PPG), HbA1c, C-peptide, HOMA-IR and fasting insulin levels.

Materials and methods: Comprehensive search of PubMed, Scopus, EMBASE and Web of Science was conducted from inception to March 2025. Eligible studies were pooled using a random-effects model to calculate weighted mean differences (WMD) or standardized mean differences (SMD) with 95% confidence intervals (CIs). Heterogeneity was assessed using I² statistics, and publication bias was evaluated using funnel plots and Egger's tests.

Results: Thirty-nine studies with 3855 participants were included. Bariatric surgery resulted in significant reductions in FBG (WMD = 3.461; 95% CI: 2.740-4.182, p < 0.001), PPG (WMD = 6.153; 95% CI: 4.298-8.007, p < 0.001) and HbA1c levels (WMD = 2.085; 95% CI: 1.561-2.608, p < 0.001). Modest but non-significant improvements were observed in C-peptide (SMD = 0.358; 95% CI: -0.043 to 0.759, p = 0.075) and fasting insulin (SMD = 1.593; 95% CI: -0.392 to 3.577, p = 0.104). Significant reductions in HOMA-IR levels (WMD = 2.480; 95% CI: 1.010-3.950, p = 0.009) were noted. High heterogeneity was observed across most outcomes. Publication bias was detected for FBG and HbA1C, while it was undetected for the rest of the outcomes.

Conclusions: Bariatric surgery significantly improves glycaemic and metabolic outcomes in obese patients with T2DM. These findings support its integration into diabetes management pathways, offering a promising approach for long-term disease control and complication reduction. Further research is needed to evaluate long-term outcomes and mechanisms.