Cannabis Consumers Reportedly Gain Less Weight Than Non-users
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A new study from two researchers at Michigan State University suggests that adults who use marijuana could be less likely to be obese compared to non-users.
In the paper published in the International Journal of Epidemiology last month, researchers looked at data sets from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a cross-sectional, nationally representative study sample of American adults, to study the relationship between marijuana use and changes in body weight in respondents.
Adults who consumed cannabis gained less weight on average
The researchers identified relevant information from responses to the 2001-2002 iteration of the NESARC interviews, such as age, height, body weight, and cannabis use, as well as less obvious variables, such as ethnic self-identification, alcohol use, tobacco use, and education attainment. Eligible participants for this study were respondents who answered all questions in both the original survey (dubbed ‘Wave 1’ or ‘W1’) and a follow-up done in 2004-2005 (‘W2’). In total, there were over 33,000 eligible respondents that were reviewed as a part of this new study.
Cannabis use was split into one of four categories: ‘persistent use’, for respondents who reported cannabis use within 12 months; ‘initiation’, for those who had not used cannabis prior to W1 but had before W2; ‘discontinuation or quitting’, for those who reported some extent of use at or before W1, but had not used cannabis for 12 months prior to W2; and ‘never use’, for respondents who said they had never used cannabis in their lifetime. The changes in body weight were studied by calculating the respondents’ body mass indexes (BMI).
After excluding participants over the age of 65 (as previous research suggests that weight loss and declining BMI is expected in older people due to natural loss of muscle mass), the researchers saw that while all of the subgroups gained weight from W1 to W2, people who reported using cannabis gained weight at a lower rate than the rest of the study population.
There was also an observed gradient looking across the subgroups of ‘quitting’, ‘initiation’, and ‘persistent use’, with those in the ‘persistent use’ group showing the most attenuated BMI gain. The ‘persistent’ and ‘initiate’ cannabis user groups were also under-represented in the group of people who reported being overweight (with a BMI of over 30 kg/m2) at the time of W2.
Explaining the lower weight gain
Two main suggestions were put forward to explain this effect on BMI in cannabis users.
The first, considers the possibility that cannabis interacting with the CB1R cannabinoid receptors could be having an effect on body weight. Previously a CB1R agonist, named rimonabant, was approved in Europe for treating obesity after it was proven in clinical trials to encourage weight loss through regulating appetite and metabolism. Chronic cannabis use has been previously linked to down-regulation of CB1R, and so it is thought that perhaps this reduction in density of CB1R expression might be promoting reduced BMI gain in persistent cannabis users through a similar mechanism to rimonabant’s action.
Alternatively, the researchers also pointed to the anti-inflammatory action of the CB2R cannabinoid receptors and the widely established link between inflammation and obesity as an explanation of the lower weight gain among cannabis users compared to the rest of the study population.
Conflicting studies emphasize need for further study
The paper does note that there were a number of limitations on the study, including that the NESARC survey does not account for any variations in terms of physical activity or caloric intake. This means that it cannot be ruled out that the trends seen in this study might be down to the lifestyle and behaviors of the average cannabis user versus the rest of the population, rather than an actual medical effect caused by cannabis consumption, though previous studies have indicated that people who consume cannabis have a higher caloric intake and lower physical activity levels than non-users.
Many cannabis users anecdotally report that cannabis consumption increases their appetite, and a recent analysis of junk food sales in states with legal cannabis would support this claim. But this finding that cannabis use might curb weight gain will be comfort to more than just recreational cannabis users — medical marijuana is often touted as being a potential method of treating the weight loss that often comes with HIV and cancer treatments. If the underlying mechanism for cannabis’ effect on body weight can be properly characterized, it might lead to a more effective medical solution for these kinds of patients.