Key result
Post-bariatric weight loss composition shows no overall MACE link, but high muscle loss raises older-patient risk.
Why the study?
Metabolic-bariatric surgery reduces cardiovascular events and mortality, but whether this benefit depends on weight loss composition was unclear.
Does high total weight loss or disproportional fat-free mass loss increase the risk of MACE and all-cause mortality in patients following metabolic-bariatric surgery?
Cohort (n=5,889)
No
Does high total weight loss or disproportional fat-free mass loss increase the risk of MACE and all-cause mortality in patients following metabolic-bariatric surgery?
Excessive total weight loss and disproportional fat-free mass loss (≥30%) at 12 months post-bariatric surgery are associated with an increased risk of MACE and mortality in patients aged 45 and older, challenging the notion that more weight loss is always better.
Caution advised for high fat-free mass loss proportion in older metabolic-bariatric surgery patients; leaves open independent effects overall and requires prospective validation.
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.
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Nuijten et al. (2025) conducted a cohort in Severe obesity (n=5,889). High proportion of fat-free mass loss within weight loss (≥30%) vs. Low-to-moderate fat-free mass loss (<30%) was evaluated on Composite of major adverse cardiovascular events (MACE) and all-cause mortality (p=0.006). In patients undergoing metabolic-bariatric surgery, weight loss composition was not independently associated with major adverse cardiovascular events or mortality overall, though a high proportion of fat-free mass loss (≥30%) increased risk in those aged ≥45 years.
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