While the effects of cannabis upon hunger pangs are well documented, precisely how “the munchies” affect weight gain is still being studied.
They call them “the munchies.” They’re the THC-induced desire to eat, well, just about anything but most typically some sort of junk food. If you watch the movies, the munchies are probably one of the most well-known parts of cannabis use lore. Of course, if you are taking something that gives you an appetite far above normal, it is going to make you gain a bunch of weight, right? Well, no, it doesn’t. As is such a common theme in discussions of cannabis, the obvious answer is not the correct one.
At this point, you might be thinking, “That I can’t be right.” You’ve eaten an entire pan of brownies after using cannabis and the only thing stopping you from eating more was that the last crusty corner piece was finally gone. That part is correct. THC is an agonist (activator) of the CB1 receptor, and this receptor plays a large part in our short-term hunger signaling. The munchies are real. What isn’t real is that cannabis is typically a cause of longer-term weight gain.
The scientific evidence is piling up showing cannabis generally reduces body weight. My suspicion is that cannabis generally trends the adult person to a more normal, homeostatic weight. Considering that these studies were done in our current environment of an obesity epidemic, it is not a surprise that cannabis appears to be associated with weight loss. A recent metanalysis of several studies with over 156,000 patients showed 7 percent lower average body mass index (BMI) in cannabis users despite the fact that cannabis users reported eating 800 more calories per day. Studies in specific adult groups such as the morbidly obese, those with psychosis on antipsychotic medications and specific racial groups such as the Inuit also showed similar weight loss in cannabis users. The study of patients on antipsychotic medications also showed improved cholesterol levels that worsened in the patients that stopped using cannabis.
A warning for teens or parents of teens if you are reading this: Cannabis is not helpful for weight loss in that age group. While development is still occurring, that is a different homeostatic situation. A 2010 study of students 11-17 years old found an association between cannabis use and obesity in girls. A second 2013 study found that cannabis use in the teen years was associated with a higher incidence of obesity in the late teens and early 20s.
The first question is, How does cannabis do this? The second question is, Can we use it to our advantage? Thus far, it has been mainly a surprising and pleasant side effect. Unfortunately, we don’t have clear answers to these questions yet. The simple idea is if THC activates the receptor and makes you hungry, if we block the receptor, you won’t be hungry anymore. Unfortunately, simplicity is not the case with cannabis and weight loss. Pharmaceutical companies tried, and it failed miserably. Sanofi-Aventis, the large French multinational drug company, created a CB1 receptor blocker on the premise that if THC activates this receptor and it makes you very hungry, then a receptor blocker would suppress appetite. They created a drug called Rimonabant that did exactly this and did make people lose weight. It was approved in Europe and Mexico, but not in the US. However, it did not last long on the market, as psychiatric side effects including suicide, depression and anxiety were far too common. This would not be a surprise to people who use cannabis to treat those disorders.
They were possibly on the right track but did not take into consideration all of the effects of the plant. For example, it is known that in addition to THC being a receptor agonist, there are other molecules in the plant that can act to block the receptor and suppress appetite. THCV (tetrahydrocannabivarin) is the most studied of these. THCV can be an agonist of the receptor and an antagonist (blocker) at other concentrations. This explains how the psychiatric symptoms associated with a full receptor blocker like Rimonabant are avoided by the natural molecules. Even the activation of the receptor by THC itself appears to cause hunger in the first few hours after activation, but appetite suppression is the activity of the receptor over a longer time. Cannabinoid receptor physiology is very complex. We are still learning the details. Science only discovered this receptor system in our bodies in 1988. While that might seem like a long time ago, it really is not in the world of science.
There could be further ways to manipulate this system to provoke weight loss more significantly. There are cannabinoid receptors in many of the organs of our bodies, including adipocytes (fat cells). Most see fat cells as just “dumb” storage depots for excess calories, but the reality is that these are complex cells that create enzymes, hormones, proteins and other growth factors that play a large part in the regulation of our energy homeostasis. In mice, scientists have found that if they block the cannabinoid receptors specifically on the adipocytes with molecules that cannot cross into the central nervous system, weight loss can be achieved without the neuropsychiatric effects. They have not yet created such a molecule for human physiology.
Our bodies have two phenotypes of fat: white fat and brown fat. White fat is more common and what we typically think of as fat. Brown fat tends to be more abundant in people of lower body weight and in children. Brown fat uses large amounts of energy to help keep us warm so is more metabolically active than white fat. In an in-vitro study (outside the body), CBD was shown to convert white fat cell lines to the brown fat phenotype. This finding would need to be replicated in vivo (in the body) but does hint at another method in which cannabis can produce weight loss.
In another study helping to combat the mouse obesity epidemic, mice were fed a “Western diet” to the point of obesity and normal weight mice were given THC. They found that the obese mice lost weight but the normal weight mice did not. That is no surprise, but the interesting finding of the study was that the gut microbiota, the ecosystem of bacteria that live within our gastrointestinal tract, also changed with THC. The gut microbiota is influenced by our diet, as the bacteria feed on the foods we ingest. “Western diet”-type foods have been implicated in adverse changes in the gut microbiota, which actually causes more calories to be obtained from foods and leads to further weight gain. In this study, the addition of THC kept the gut microbiota of the obese mice fed a “Western diet” from changing to the less helpful types of bacteria. THC kept the gut microbiota more like the microbiota of the normal weight mice.
In addition to its actions at the receptors, adipocytes and gut microbiota, there are also other potential ways in which cannabis induces weight loss. A 2014 study in Health Economics looked at the effects of medical marijuana laws on body weight, physical wellness and exercise. Interestingly, they found age-associated causes of decreased BMI with cannabis use. In the younger (18-24-year-olds) cohort, the decrease in weight is associated with a 3.1 percent reduction in alcohol use. They attributed some of the weight loss to limited alcohol since it is a high-calorie content product. In the older cohort, the reduction of BMI appeared to be due to increased physical activity due to improved physical health, pain control and wellness.
The skeptical among you are probably thinking about the indication of cannabis for patients with cachexia (severe underweight) from diseases such as cancer or HIV. How can studies show that cannabis helps them gain weight while other studies show cannabis helping others lose weight? That doesn’t seem logical. However, if you look at the mechanism of cannabis, it is merely supplementing the endogenous molecules of our endocannabinoid system that help us maintain normal weight. Therefore, the effects are going to move the patient toward homeostasis, not further away.
In summary, at this point, we have evidence that cannabis use is associated with lower weight in the adult population. We have had some unsuccessful attempts to take this finding and create a specific medication. And finally, we have some basic science that points to several possible mechanisms that could explain the effects. How about right now? What if I want to use cannabis right now for weight loss? You can Google “cannabis weight loss” and find many strains suggested to be the best ones for weight loss. But that is mostly based on having THCV in them and user opinion. There is no science yet showing one strain to be better than another. Given the lack of known evidence at this time, I believe a product with moderate amounts of THC, CBD given its effect on adipocytes, and THCV is a reasonable place to start.
Is cannabis the panacea that will fix our obesity epidemic? That is unlikely. There are many difficult factors in this issue, and there isn’t going to be one simple solution. But with time and better understanding, I do think there are bright possibilities for this to be a safer tool in the process than much of what we do now.