Marijuana use does not affect weight loss or complication rate after bariatric surgery

Introduction: Marijuana use has been legalized in several states. It is unclear if marijuana use affects weight loss outcomes or complication rates following bariatric surgery. The purpose of this study was to determine if patients who use marijuana had higher complication rates or lower weight loss compared with non-users. Methods: All patients at a single institution who underwent primary bariatric surgery between July 2015 and July 2020 at a single institution after the legalization of marijuana within the jurisdiction were included. Data regarding marijuana use, weight and complications were abstracted retrospectively. Differences between groups were evaluated with Wilcoxon Rank-Sum tests and Fisher Freeman Halton test. Trends for marijuana use over time was evaluated with simple linear regression on summary data. Results: 1107 patients met inclusion criteria. 798 (73.3%) were never users, 225 (19.4%) were previous users, and 84 (7.2%) were active users. The proportion of active users and previous users increased over time, with significantly more prior marijuana use reported in more recent years (p = 0.014). Active users had significantly higher pre-procedural BMIs than never users: 48.7 vs. 46.3 (p = 0.03). Any marijuana use (active and previous users) was associated with higher preoperative weight compared to never: 136.4 kg vs. 130.6 kg (p = 0.001). Overall complication rate was low in all groups, and there was no difference in the rates of any complications. Active and previous users tended to lose less weight than never users, but this was not statistically significant (p = 0.17). Conclusions: Active and prior marijuana users tend to have higher BMIs on presentation, but use was not associated with complications or percent weight loss. The incidence of patient reported marijuana use is increasing in the study population. More studies on the effects of marijuana use in this patient population are warranted.