Fact #1: Cannabis use increases caloric intake. Fact #2: Cannabis users on average have lower BMI’s (body mass index) and smaller waistlines than non-cannabis users.
Initially, these statements appear to conflict on a basic logical level. With “the munchies” being frequently referenced in popular culture, and with some of the first medical cannabis approvals hinging around appetite stimulation, it’s no secret that cannabis can cause users to eat more than intended. Increased caloric intake should mean increased weight gain. So in what world are these two facts compatible? The answer is…our world.
Although weight does relate to caloric intake, ultimately the calories stored in the body depend on how completely the body has turned incoming food into usable energy, a process referred to as metabolization. In large data-based studies, researchers have noticed that cannabis users on average have lower BMI’s and smaller waistlines, which means they are less likely to be obese than non-cannabis users. Until recently, this fact has been viewed as a quirky, unexplained observation. Although data-based studies are wonderful for checking the validity of general correlations, once the data is exhausted, the track is dead. Without more data concerning metabolism specifically, researchers were not sure where to go next.
However, in 2013, one research group, from the Harvard School of Public Health, focused on this research target and added another variable to the mix: blood samples. Blood samples allow blood sugar and insulin levels to be measured, which then allows a live read of how bodies are distributing energy. Glucose is released by the body into the bloodstream to supply energy. Insulin causes this energy to be taken out of the bloodstream and stored. Through this basic exchange (including other hormones), the body attempts to keep blood sugar levels within a set range, deviating during moments of stress, such as illness or excitement. Illnesses result when the body is unable to keep a healthy balance. Diabetes, for instance, results when individuals do not produce enough insulin naturally or are insulin-resistant (IR), meaning that blood sugar is not able to decrease when needed. This resistance to insulin can be roughly calculated by using a formula that takes into account glucose and insulin levels after fasting or after the body has had plenty of time to settle after a blood sugar spike.
In the initial study, 4,657 patients gave blood samples, as well as answered the NHANES survey. A survey which is administered by the National Center for Health Statistics and that uses a statistical model to select a nationally based representative sample of individuals.This study included a large population that can be thought of as fairly diverse and representative of the U.S. at large. In assessing cannabis use, the study formed three categories: non-users, participants that had used cannabis at least once, and participants that had used cannabis in the past month. Researchers then compared blood samples to reported cannabis use. To ensure that the correlation observed would not be affected by confounding factors, researchers initially controlled results for age, sex, ethnicity, education level, income, marital status, tobacco use, physical activity level, and alcohol use. During this first round, researchers found that cannabis users displayed decreased insulin resistance, meaning a lower likelihood of developing diabetes and lower levels of insulin needed to manage blood sugar. However, as previously discussed, researchers also noticed a lower BMI among cannabis users. BMI can also affect insulin resistance as the body adjusts to re-set weight, which means that cannabis might only have been achieving insulin modulation through impacting BMI. In that case, anything that affects BMI would be as effective as cannabis at changing insulin resistance. However, even after controlling for BMI, the correlation between cannabis use and decreased insulin resistance was statistically significant, with cannabis users having 16% lower fasting insulin levels and 17% lower insulin resistance (HOMA-IR). Participants that had used cannabis within the past month had even lower insulin resistance than those who had merely used at least once, which would seem to indicate that the effect has something to do with the level of cannabinoids currently circulating the body.
While this study provides a strong initial data point, more studies over different populations will be needed to determine in what specific situations the relationship holds. Earlier this year, another study essentially repeated the experiment among the Inuit population of Canada. Although this may seem like a very bizarre choice of test population, the study was actually very clever; Inuit people have been observed to have lower rates of diabetes than both Canadians at large as well as other similar indigenous populations. For this reason, researchers hope to find a genetic or lifestyle difference among the population that holds the answer to reducing cases of diabetes. As expected, researchers found a correlation between cannabis use and decreased body mass index as well as cannabis use and decreased insulin resistance. However, this time, after controlling for BMI, the impact on insulin resistance disappeared. This would seem to indicate that cannabis has no direct effect on insulin levels. However, some care must be taken in evaluating these results. First, the population is one that specifically has lower rates of insulin resistance. Secondly, the population has an astoundingly high obesity rate (49%), meaning that the BMI distributions here are not representative of most populations.
Finally, a third study has emerged from France this month that extends the data to an HIV and Hepatitis C (HCV) positive population. In this study, researchers sampled a database of 703 patients with both HIV and HCV. This population is unique in that both diabetes frequency and cannabis use are abnormally high, and as a result, this population serves as a nice counter-point to a diabetes-resistant population such as the Inuit. In this study, with a procedure essentially identical to the first study, researchers controlled for various socio-economic and lifestyle factors and found a correlation between cannabis use and decreased insulin resistance…even after controlling for BMI. Why would this be different than the Inuit population? Certainly the population was more ethnically diverse. BMI rates were also lower and closer to the average U.S. population.
Even beyond differences in population, at this point in time, we really don’t know why metabolic effects are occurring from cannabis use. Researchers have postulated that the interaction between the endocannabinoid system and the body’s metabolism occurs through partial antagonism of CB1 receptors in the brain. This speculation stems from trials in which Rimonabant and other CB1 receptor antagonists have been shown to reduce body mass. However, drinking coffee regularly has also been shown to reduce insulin resistance, and no ingredient in normal coffee activates endocannabinoid receptors. To date, no one has fully elucidated how insulin resistance is modified. However, we notice that in all of these studies, as well as others, cannabis users are less likely to be obese. This can only mean that either cannabis is causing users to consume less as a whole despite episodes of binging or that cannabis is up-regulating the metabolism somehow. Either effect is possible, and either seems to be a welcome side effect for medical cannabis patients.
M.P. Carrieri, L. Serfaty, A. Vilotitch, M. Winnock, et. al. (2015) “Cannabis use and reduced risk of insulin-resistance in HIV-HCV infected patients: a longitudinal analysis.” Clinical Infectious Diseases Advance Access published 16 March 2015.
Elizabeth Penner, Hannah Buettner, Murray Mittleman. (2013) The Impact of Marijuana Use on Glucose, Insulin, and Insulin Resistance Among US Adults. The American Journal of Medicine (2013) 126, 583-589.
Gerard Ngueta, Richard E. Belanger, Elhadji Laouan-Sidi, et. al. (2015) Cannabis Use in Relation to Obesity and Insulin Resistance in the Inuit Population. Obesity Biology and Integrated Physiology (2015) 23, 290-295.