BackgroundBariatric surgery (BS) is the most effective intervention for severe obesity, leading to sustained weight loss, reduced obesity-related comorbidities, and cardiovascular mortality.AimTo assess changes in high-density lipoprotein (HDL) functions [cholesterol efflux capacity (CEC) and anti-inflammatory capacity] at different follow-up times in patients with severe obesity undergoing BS.MethodsA prospective observational study within a cohort of consecutively enrolled patients with severe obesity scheduled to undergo BS. In total, 62 participants (77% women), with a mean age of 42.1 years (SD 9.33 years) underwent BS. Regarding the surgical procedure, 27 (43.5%) underwent sleeve gastrectomy and 35 (56.5%) Roux-en-Y gastric bypass. All patients were evaluated preoperatively and at 1, 3, 6, and 12 months after surgery.ResultsA decrease in body mass index and an improvement in the systemic lipid profile, indicated by reductions in total cholesterol, low-density lipoprotein cholesterol (LDLc), and remnant cholesterol, and an increase in HDL cholesterol (HDLc) was observed (all p trend < 0.001). Time-series comparisons vs. baseline showed that, in general, anthropometric measures, glycemia, total cholesterol, LDLc, and remnant cholesterol decreased at all follow-ups, whereas HDLc and triglyceride concentrations significantly improved vs. baseline from 6 months, reaching at 12 months the highest HDLc levels (29.6%, p < 0.001) and the lowest circulating triglycerides (−30%, p < 0.001). Although HDL's anti-inflammatory ability worsens after surgery, the HDL-mediated CEC linearly increased after surgery (for both p trend < 0.013).ConclusionBS improves the lipid profile both quantitatively and qualitatively after 1 year, specifically enhancing HDL-mediated cholesterol efflux capacity, which may contribute to a reduced cardiovascular risk in individuals with severe obesity.