This coming July 1st (2018) will not only be Canada Day, but it will also mark the legalization of marijuana (aka pot, weed, cannabis) in Canada. While we have the occasional patient ask us if smoking marijuana is okay after bariatric or weight loss surgery, we anticipate that this question will become much more common once it becomes legal.

Here are our thoughts on the topic….

Regardless of how marijuana is taken (i.e. smoked, inhaled or eaten) the effects are the same. The majority of people who use marijuana describe a sensation of relaxation and euphoria (the “high”). Some people however react badly to the drug which can result in a state of panic, anxiousness and fear, or in some cases even hallucinations if they take too much.

Of particular relevance to bariatric or weight loss surgery, is the fact that marijuana impacts the part of your brain that controls appetite. Have you heard of the “munchies”? Yep, that’s right, the “munchies” are a real thing! Marijuana can increase your appetite, causing you to eat more, which obviously is not great if your goal is weight loss.

Interestingly, a recent study on weight and marijuana use actually showed that marijuana use may very slightly (and we mean VERY slightly) reduce body weight (about a 0.5% reduction in BMI) (1). This study however was conducted on a group of people with an average BMI of 27 kg/m2, which is way below the average bariatric or weight loss surgery patients’ BMI pre-surgery. This unfortunately means that this mild weight loss effect cannot be applied to the typical bariatric or weight loss surgery patient.

We did however find one recent study done in 2016 that is more relevant to the bariatric or weight loss surgery population (2). The study was run on a group of 50 patients (62% being RYGB patients) all 2 years after surgery. The results of the study showed that the patients who had smoked marijuana within the last 30 days and the patients who had started smoking more since surgery, were all more likely to have disordered eating habits, specifically “loss of controlled food intake” (2). Although the study did not look at weight outcomes related to marijuana use, we know that disordered eating habits such as grazing and bingeing are risk factors for weight regain after bariatric or weight loss surgery.

We asked a Canadian-based bariatric surgeon for his opinion on the subject of marijuana use after surgery. Here is what he said:

“Although currently there is a lack of available research on the effects of marijuana on the bariatric surgery population, there are a few concerns to note. Regular marijuana use could increase the risk of postoperative complications including bleeding, infection and pulmonary embolism. Secondly, THC increases feelings of hunger, thus the degree of weight loss post-surgery may suffer due to continued marijuana use.” Dr. Simon Chow, Bariatric Surgeon, MD MSc FRCSC FACS

In conclusion, we do not yet fully understand the effects of marijuana use after surgery with respect to weight loss and longer term weight maintenance outcomes. The field of research is still very young (3). Regular marijuana use however may pose medical risks after surgery, therefore speak with your surgeon if you have been prescribed marijuana for medical reasons. Furthermore, if you choose to use marijuana for recreational reasons on a regular basis, it is worth discussing this habit with your bariatric nurse and dietitian.

– Monica & Lisa

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