Continuous aerobic exercise and atherosclerosis-related vascular indices in overweight and obese adults: a Bayesian three-level meta-analysis of randomized controlled trials

Background: Overweight and obesity accelerate vascular aging and atherosclerosis-related processes through endothelial dysfunction and increased arterial stiffness. Whether continuous endurance training (CET) improves key vascular functional and structural indices in overweight/obese adults remains uncertain, and evidence synthesis is complicated by correlated effect sizes within trials. Objective: To quantify the effects of CET on flow-mediated dilation (FMD), pulse wave velocity (PWV), and carotid intima-media thickness (CIMT) in overweight and obese adults using a Bayesian three-level meta-analysis of randomized controlled trials (RCTs). Methods: PubMed, Web of Science, Cochrane Library, Embase, APA PsycINFO, and EBSCO-SportDiscus were searched from inception to November 2025. Eligible studies were RCTs enrolling adults (18-65 years) with overweight/obesity, comparing CET with usual care/usual lifestyle, and reporting baseline and post-intervention data for FMD, PWV, or CIMT (≥4 weeks). Standardized mean differences (SMDs) for between-group changes were synthesized using a Bayesian three-level random-effects model to account for within-study dependency. Risk of bias was assessed with RoB 2, and certainty of evidence with GRADE. Results: Seventeen RCTs (746 participants) were included. CET improved FMD (13 studies, 14 effect sizes; μ = 1.14, 95% credible interval [CrI] 0.42 to 1.95), with substantial between-study heterogeneity. CET reduced PWV (7 studies, 9 effect sizes; μ = -0.23, 95% CrI -0.41 to -0.06) with minimal heterogeneity, indicating a consistent benefit on arterial stiffness. The effect on CIMT was not conclusive (5 studies, 5 effect sizes; μ = -0.23, 95% CrI -0.66 to 0.18). Exploratory subgroup analyses suggested the most consistent improvements clustered around interventions lasting 9-12 weeks and performed three sessions per week. GRADE certainty was low for FMD, moderate for PWV, and very low for CIMT, mainly due to risk of bias and imprecision. Conclusions: In overweight and obese adults, CET yields a "function-first" vascular response-improving endothelial function (FMD) and reducing arterial stiffness (PWV)-while evidence for short- to mid-term structural change in CIMT remains insufficient. Future well-designed RCTs with longer follow-up and standardized vascular assessments are needed to clarify CET effects on vascular remodeling. Systematic review registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42024593701.