For a study, the researchers evaluated the security of sleeve gastrectomy and gastric bypass surgery in a large cohort of commercially insured bariatric surgery patients using the IBM MarketScan claims database while accounting for measurable and unmeasurable causes of selection bias in who was chosen for each procedure. Sleeve gastrectomy has quickly become the most popular bariatric procedure in the United States. Still, its long-term safety was unknown, and the risk of developing acid reflux and the need for revision surgery may be higher than previously assumed. Small sample size (in randomized trials) and selection bias have restricted previous studies comparing sleeve gastrectomy to gastric bypass (in observational studies). From 2011 to 2018, instrumental variables analysis of commercially insured patients in the IBM MarketScan claims database. From 2012 to 2016, investigators looked at patients who had bariatric surgery. Using Comprehensive Procedural Terminology and International Classification of Disease (ICD)-9/10 codes, they detected re-interventions and complications 30 days and 2 years after surgery. To account for unmeasured confounding, the study group used the previous year’s sleeve gastrectomy utilization in each state as an instrumental variable, using the variance in payers’ decisions to cover sleeve gastrectomy as a natural experiment. Between 2012 and 2016, the percentage of patients who had a sleeve gastrectomy increased from 52.6% to 75% among 38,153 patients who had bariatric surgery (2016). In addition, patients who had sleeve gastrectomy had fewer re-interventions (sleeve 9.9% vs bypass 15.6%, P=0.001) and complications (sleeve 6.6% vs bypass 9.6%, P=0.001), as well as lower overall healthcare spending ($47,891 vs $55,213, P=0.003), than patients who had a gastric bypass at 2 years. However, revisions were somewhat more likely in sleeve gastrectomy than in gastric bypass at the 2 years (sleeve 0.6% vs bypass 0.4%, P=0.009). Even when selection bias was considered, sleeve gastrectomy exhibited a better safety profile than gastric bypass up to 2 years after surgery in a large cohort of commercially insured patients. The greater risk of revisions in sleeve gastrectomy, on the other hand, warrants additional investigation.