Many people agree that cannabis influences a person’s appetite, but some research suggests the effects on people who chronically use may be the opposite of what popular media depicts. Rather than boost a person’s consumption of food, researchers at the University of Colorado Anschutz School of Medicine are investigating whether cannabis might reduce the appetite of frequent, long-term users.
Studies have shown that long-term cannabis users generally have a lower body mass index (BMI) compared to non-users. To better understand why that is, J. Megan Ross, PhD, an associate professor in the CU Anschutz Department of Psychiatry who specializes in substance use, is investigating how cannabis affects appetite and gut health.
“Most people assume the opposite would be true, because everyone knows about the munchies, but that’s not what we’re seeing in those who use frequently and persistently. It’s fascinating,” Ross says.
She explains that it is important to understand how cannabis affects appetite because some people, such as people with gastrointestinal disorders, may be using medical marijuana in hopes of increasing their appetite.
“It’s unclear how cannabis affects our gastrointestinal function,” Ross says. “We need to figure that out and share information with the public so they can really understand whether cannabis may be helpful to them or not in boosting their appetite.”
Investigating the influence on diet and appetite
One of Ross’ latest studies, published in the Drug and Alcohol Dependence journal, was a preliminary exploration of the associations between cannabis use frequency and appetite — as well as eating behaviors and BMI — among pairs of twins. Each of the 90 participants, who were between the ages of 21 and 55, reported using cannabis at least once a week.
The participants are involved in a longitudinal study that Ross is conducting in which one twin ceases using cannabis for six weeks while the other twin continues their regular use of cannabis. At the end of six weeks, the investigators will compare different outcomes between the two twins, such as mental health and cognitive function.
“A co-twin control design is helpful because these twins share genetics and likely grew up in the same environment, which helps us control for different variables that may affect their outcomes,” Ross says.
Before the six-week study began, the researchers collected baseline data from participants, including questionnaires about their nutrition and eating behaviors.
The researchers found that there were significant “between-family effects,” meaning that there were notable differences between families.
“We saw that in families who had higher levels of cannabis use, they ate fewer meals per day, ate a less healthy diet, and reported a lower appetite,” Ross says.
When comparing participants with their own twin, the researchers found no significant effects between cannabis use frequency and eating fewer meals per day or eating a less healthy diet. However, Ross notes that there are some limitations in the study, including a smaller sample size, which may result in the study not detecting smaller effects of cannabis.
Ultimately, Ross and her co-authors concluded in this study that there was not a causal relationship between cannabis use frequency and eating behavior, nor was there a causal relationship between cannabis use frequency and diet. The results indicate the association between cannabis use and eating behavior may be explained by shared genetic and environmental factors.
“The data suggests to me that cannabis use is not what caused participants to eat fewer meals per day or eat a less healthy diet,” Ross says. “The association between cannabis use and appetite is more complex.”
The findings do not conclusively show that more frequent cannabis use is associated with a lower appetite — the study may not have been powered to detect these smaller effects — but the preliminary data does appear to support that theory, Ross explains.
“If more frequent cannabis use is associated with a lower appetite, this might explain why we see a lower BMI among long-term cannabis users. But even if that’s the case, we don’t know why that is happening and if cannabis is causing that to happen,” she says. “We're really interested in figuring it out.”
Ongoing research to untangle a complex issue
Based on the preliminary study, Ross and her co-authors explain that future research with larger sample sizes and longitudinal designs are needed to further explore how long-term cannabis use may impact appetite, as well as appetite-related hormones such as glucagon-like peptide-1 (GLP-1).
“We’ve designed a larger research grant that will look at objective outcomes including how cannabis use frequency affects actual food intake and appetite hormones,” Ross says. “We are finalizing our findings from our longitudinal study in which one twin abstained from cannabis for six weeks while the other twin continued using. That is forthcoming.”
Ross is also working on a research grant to study cannabinoid hyperemesis syndrome — also referred to as “scromiting” (combination of screaming and vomiting) — in which severe, recurring episodes of nausea and vomiting are associated with chronic use of marijuana.
“This syndrome is on the rise in emergency rooms. Some speculate that higher potency cannabis products are linked to it,” she says. “There is also a prodromal phase to that syndrome where people can have regular nausea and abdominal pain without vomiting. I hope to pinpoint where and when we might see that effect.”
These investigations to untangle how cannabis affects people’s gastrointestinal function and appetite are critical given the spread of higher potency cannabis products and the popular belief that cannabis boosts appetite — a common assumption that may end up being incorrect.
“There is much that we still need to learn,” Ross says. “We need more information to really understand how cannabis affects people and in what context it can be helpful for patients.”
