The impact of morbid obesity and metabolic syndrome in elective spine surgery outcomes: A systematic review

Background Morbid obesity is increasingly common among patients undergoing elective spine surgery and is associated with substantial technical and physiological risk. By 2030, nearly 1 in 2 US adults is projected to have obesity, and severe obesity is expected to affect almost 1 in 4 adults. This systematic review synthesizes the available evidence on morbid obesity (BMI ≥ 40 kg per m2) and metabolic syndrome in elective spine surgery and summarizes complication patterns, resource utilization, and patient-reported outcomes (PROs), with attention to whether surgical approach potentially modifies risk.Methods MEDLINE, EMBASE, Scopus, Web of Science, and the Cochrane Library were searched from January 1, 2000 through September 30, 2025 for comparative adult studies of elective spine surgery in morbidly obese versus non-obese patients. Two reviewers screened studies and extracted data. Risk of bias was assessed with ROBINS I, and reporting followed PRISMA guidance. Because outcome definitions, procedures, and data sources were heterogeneous, we primarily performed a structured qualitative synthesis and, where available, reported pooled estimates from the most comprehensive available meta-analyses as quantitative benchmarks.Results Thirty-six studies were eligible. In the largest published meta-analysis from Jiang et al., 2014, morbid obesity was associated with higher odds of surgical site infection (Odds ratio [OR 2.33]), venous thromboembolism (OR 3.15), revision surgery (OR 1.43), and mortality (OR 2.6). A contemporary anchor-validation pool of 2 post-2014 cohorts with extractable surgical-site-infection data yielded a concordant estimate (pooled OR 3.03, 95% Confidence Interval [95% CI 2.20-4.17]; I² = 0%). Metabolic syndrome remained an independent predictor of wound complications (OR 1.47) and readmissions (OR 1.48) after adjustment for obesity. Although obese patients improve after surgery, the likelihood of achieving minimal clinically important difference (MCID) threshold in patient reported outcomes is often reduced. Evidence on preoperative bariatric surgery was mixed, and emerging pharmacologic optimization with GLP-1 receptor agonists warrants further study.Conclusions Morbid obesity and metabolic syndrome are strong predictors of adverse perioperative outcomes and increased resource utilization after elective spine surgery. A value-based approach should incorporate metabolic health into risk stratification and emphasize scalable, equitable optimization pathways.