Marijuana has always been known to alter certain brain activity that controls appetite, causing what is more commonly known as the munchies, but can cannabis actually contribute to weight gain? Some studies believe that this isn’t the case; for example, a 2013 study published in The American Journal of Medicine found that marijuana may improve insulin control, ultimately regulating weight gain to help users lose weight.

A new study conducted by researchers of the University of Montreal at the CHUM Research Centre suggests it’s a little more complicated than that. “It is known — and often reported by users — that cannabis causes temporary increase in appetite. As to whether it actually causes weight gain in the long term, the available data is limited. The question is all the more difficult to answer since many other factors can influence weight,” said Professor Didier Jutras-Aswad in a recent press release. “For instance, cannabis use may be associated with cigarette smoking, which also alters appetite, and many effects of cannabis vary by gender and level of use.”

Jutras-Aswad says that during the study, the team of researchers paid special attention to outside facts that could influence weight gain, both related and unrelated to marijuana use. They ultimately found that weight gain is most affected by long-term use, in addition to gender, the level with which cannabis is used and whether or not the person smokes cigarettes.

Researchers found varying degrees of weight gain with different combinations of these factors. “Specifically in male non-cigarette smokers, greater cannabis use led to greater weight gain. And significantly, in male cigarette smokers, the effect was almost the opposite,” Jutras-Asward said.

In order to discover how different components affect weight gain in marijuana users, researchers pulled data from the Nicotine Dependence in Teens (NDIT) study, conducted by Jennifer O’Loughlin. The study surveyed 1,294 different people, starting at ages 12 or 13, and asked them each year about their diet, overall mental and physical health which included weight and height, degree of physical activity, amount of cannabis use, alcohol use and nicotine use. Jutras-Aswad believes the NDIT’s detailed analysis of outside factors allowed for the perfect set of data to discover to which degree each factor contributes to weight gain. “The NDIT study provided us with the opportunity to have detailed longitudinal data to better respond to a research question requiring consideration of several factors simultaneously,” he said.

Even though researchers were able to observe differences between weight gain among the sexes, they are still not sure why these differences exist, but they have a theory. “THC and nicotine do not affect the neurobiological circuits controlling hunger in the same way in men and women,” Jutras-Aswad said. “We also know that during these targets in the brain are modified by hormonal factors that can fluctuate, in particular during menstrual cycles.” Jutras-Aswad also said psychological differences could potentially contribute to this inconsistency in weight loss; each gender perceives weight gain differently.

Researchers believe their study is equipping health care professionals with the information necessary to teach their patients how cigarette smoking, and cannabis abuse contribute to weight gain, as well as how these risks differ among genders. Jutras-Asward notes that because the study was able to determine what factors contribute to weight gain in cannabis users, it can shed some light on other potential health problems that come with cannabis-associated weight gain.

Jutras-Aswad concluded by saying, “Regarding interventions with the population, one of the findings to keep in mind is that when a person uses cannabis they also often report using tobacco. When one substance is used, another one is often consumed. We must therefore be able to prevent, detect, and intervene in the problematic use of several substances simultaneously.”

Source: Dube E, Jutras-Aswad D, O’Loughlin J, et al. Cigarette smoking may modify the association between cannabis use and adiposity in males. Pharmacology, Biochemistry, Behavior. 2015.

Penner E, et al. The Impact of Marijuana Use on Glucose, Insulin, and Insulin Resistance among US Adults. The American Journal of Medicine. 2013.