Post-surgical cannabis use is associated with weight loss among individuals up to 4 years after bariatric surgery

Introduction: Although cannabis is known to stimulate appetite, it is not clear whether cannabis use may impact weight loss outcomes following bariatric surgery. Although some work has suggested that pre-surgical cannabis use is not associated with post-surgical weight loss, the role of post-surgical cannabis use has not yet been examined. The purpose of this study was to measure pre- and post-surgical cannabis use and determine whether cannabis use was associated with weight loss outcomes following bariatric surgery.

Methods: Patients who underwent bariatric surgery over a 4-year period at a single health care system were invited to complete a survey regarding pre- and post-surgical cannabis use and report their current weight. Pre-surgical weight and BMI were extracted from medical records to calculate change in BMI (ΔBMI), percent total weight loss (%TWL), percent excess weight loss (%EWL), whether participants experienced a successful weight loss outcome, and whether participants had weight recurrence.

Results: Among all participants (N = 759), 10.7% and 14.5% engaged in pre- and post-surgical cannabis use, respectively. Pre-surgical cannabis use was not associated with any weight loss outcomes (p > 0.05). Any post-surgical cannabis use was associated with lower %EWL (p = 0.04) and greater likelihood of weight recurrence (p = 0.04). Weekly cannabis use was associated with lower %EWL (p = 0.003), lower %TWL (p = 0.04), and a lower likelihood of having a successful weight loss outcome (p = 0.02).

Conclusions: Although pre-surgical cannabis use may not predict weight loss outcomes, post-surgical cannabis was associated with poorer weight loss outcomes. Frequent use (i.e., weekly) may be especially problematic. Providers should consider screening patients for cannabis use and educate them about the potential impact of postoperative cannabis use on weight loss following bariatric surgery.