Association of Weight Loss Composition Following Metabolic‐Bariatric Surgery With Incident Major Adverse Cardiovascular Events and All‐Cause Mortality

Severe obesity is associated with an increased cardiovascular risk. Metabolic‐bariatric surgery (MBS) can reduce the risk of cardiovascular events and mortality, potentially depending on weight loss composition. This study assessed the association between post‐MBS weight loss composition and major adverse cardiovascular events (MACE) and all‐cause mortality. This retrospective, single‐center study included patients who underwent MBS between 2012 and 2020. Twelve‐month total weight loss (TWL), fat mass loss (FML), fat‐free mass loss (FFML), and proportion of FFML within weight loss (FFML/WL) were assessed. The primary endpoint was a composite of MACE and all‐cause mortality. The event rate was compared across weight composition tertiles, while adjusting for cardiometabolic medication, age, sex, preoperative weight and surgery type. In total, 5889 patients (21% men; 44.3 ± 11.1 years) were included. During a follow‐up of 4.9 ± 2.2 years, a total of 106 patients (1.8%) reached the primary endpoint. TWL, FFML, FML and FFML/WL were not associated with the composite endpoint after adjustment for confounders. Nevertheless, stratified analysis revealed that older patients (≥ 45 years) with a high TWL (HR = 1.68 [95% CI, 1.03–2.75]) and high FFML/WL (HR = 1.78 [95% CI, 1.12–2.85]) had a higher risk of MACE and all‐cause mortality. Weight loss composition was not related to MACE and mortality in the total population, but higher TWL and FFML/WL ≥ 30% at 12 months post‐MBS were associated with a worse prognosis among patients aged ≥ 45 years. The harm associated with excessive TWL and FFML post‐MBS, along with potential countermeasures, should be further investigated to optimise clinical outcomes.