, published in Innovations in Clinical Neuroscience
July-August 2014, examines the research and information available on the impact of cannabis use on body weight. Their findings are summarized here.
One of the most well-known results
of cannabis use is appetite stimulation, known commonly as “the munchies”. However, in studies on the effect of cannabis use in patients with cachexia
(“loss of weight, muscle [wasting], fatigue, weakness, and significant loss of appetite in someone who is not actively trying to lose weight”) and anorexia
(loss of appetite), often experienced by patients with HIV/AIDS and cancer, often show that cannabis use does not increase body weight (a main goal of increasing appetite, in order to improve patients’ strength and health, and ability to tolerate treatments).
Additionally, it is often found that cannabis users have a lower body mass index (BMI
) than non-users, meaning that users tend to weigh less for their given height than non-users (a low BMI indicates a low-weight individual, a “normal”/average BMI indicates a normal weight individual, and a high BMI indicates an overweight or obese individual; having a BMI higher than average may result
in certain health issues such as heart disease, diabetes, heart disease, etc. although the reliability of and ability to interpret BMI measurement is limited
in certain circumstances).
If cannabis use increases appetite, blockage of cannabinoid receptors should have the opposite effect. As expected, in animal studies that prevent
cannabinoid receptor stimulation, weight gain is prevented¹ and
. For these reasons, using cannabinoid receptor antagonists
(i.e. blocking cannabinoid receptors/preventing cannabinoid receptor stimulation) may be useful for those who are overweight or obese and trying to lose weight. However, in studies
of two CB1 receptor antagonists (rimonabant and taranabant), although use decreased weight in human participants, very negative side effects of the treatments were found, including increases in thoughts of suicide.², ³
On a different note, in a study
of 3,617 participants between 18 and 30 years old, it was found that participants with a history of cannabis use ate more calories each day, but had lower BMIs, than participants who were not cannabis users. Another study
of 10,623 participants found similar results, but found that cannabis users were also more likely to be tobacco users (meaning that the results were potentially caused by tobacco use or marijuana+tobacco use).
In another review
of two other studies, among 41,633 participants (Study 1)ª and 9,103 participants (Study
2), researchers found that obesity was more prevalent in non-users than in cannabis users: the percentage of participants who were obese and were not
cannabis users was 22.0% in Study 1 and 25.3% in Study 2, whereas the percentage of people who were obese and were
cannabis users was only 14.3% in Study 1 and 17.2% in Study 2. A study
of 2,566 young adults in Australia found similar results.
Additionally, authors of an animal study
found that when treated with whole-plant cannabis extract, obese rats gained weight more slowly than rats of normal weight. These results indicate that use of therapies that work via cannabinoid receptor stimulation may be useful for controlling obesity.
Cannabinoid therapy use may be useful for increasing weight in patients with HIV/AIDS who are suffering from cachexia or “wasting syndrome”. In 2013 alone, there were roughly 35 million people living with HIV, with more than 2 million new people infected with HIV each year.
In a review
, the author found that both smoked cannabis and the legal and FDA-approved medication comprised solely of synthetic delta-9-tetrahydrocannabinol (THC, which many patients find overly anxiety-inducing
, possibly due to the absence of other cannabinoids to dull the psychoactive impact of THC) increased appetite.
Additionally, in a study
of patients with HIV/AIDS, participants were either given (1) whole-plant cannabis to smoke, (2) dronabinol, or (3) placebo, a sugar pill/inactive substance used to “control” studies, or ensure that results of active treatment are truly applicable and not merely the result of anticipatory/expected effects (i.e. to make sure that results of treatment aren’t “all in your head”).
It was found that both whole-plant cannabis and dronabinol were able to increase weight in patients more than the placebo. Another study
also showed that whole-plant cannabis and dronabinol were able to increase weight in HIV-positive patients equivalently, and yet another
found that dronabinol increased the amount of calories eaten (although patients became tolerant to the effects, so it became less effective over time). While the sample sizes of these studies were small, the results show the potential utility of cannabinoid receptor stimulation in increasing health and quality of life for patients with HIV/AIDS.
Although a review
of the literature published in 1997 found that pure THC (such as dronabinol) was useful for decreasing nausea and increasing appetite in some instances for patients with cancer, a 6-week study
of 243 participants was ended early when researchers noted that preliminary results showed that whole-plant cannabis extract was no better than the placebo at increasing weight. Another study
of 469 participants, using dronabinol, megestrol
(a non-cannabinoid appetite stimulant) or both found that megestrol caused more weight gain than dronabinol, and using both was not more effective than using megestrol alone.
While megestrol is an effective appetite stimulant, it is also important to note that in some instances, megestrol use can induce side effects that are more serious than those caused by dronabinol/whole-plant cannabis use, including
“impotence, decreased sexual desire, unexpected vaginal bleeding… gas, rash, weakness… leg pain, difficulty breathing, sharp [and] crushing chest pain, slow or difficult speech”, etc. However, because dronabinol/whole-plant cannabis can cause
marked/intense joy (euphoria), extreme sleepiness/lethargy, and hallucinations, their use is also limited in certain patient populations, such as the elderly or those with certain mental health disorders.
Appetite Stimulation to Improve Quality of Life
Due to the fact that eating stimulates “pleasure centers” in the brain, increasing appetite is still beneficial
for patients, even with failure to increase body weight. As noted by a quote
in the review
, “[S]timulation of the [cannabinoid] receptors in the mammalian cannabinoid system specifically increases food craving and enjoyment…”
Given that humans socialize frequently over food and meals and eating food is enjoyable, improving appetite with cannabis use may make patients feel better subjectively, even if their health doesn’t objectively improve as a result. Although one goal in medicine is to increase length of survival, improving quality of life for patients, especially those for which increasing survival is unlikely or impossible, is an equally important issue.
Why the Mixed Results?
The authors note that possible reasons for the mixed results summarized here include:
- a difference in results depending on dose (no increase in eating with one cannabis cigarette, notable increase in eating [snacks, rather than meals] with 2-3 cannabis cigarettes)
- a difference in results depending on frequency of use (short-term –> weight gain, long-term –> no weight gain)
- the possibility that cannabis users also use other recreational substances
- the fact that both food and cannabis use “compete” for receptors in reward/pleasure centers of the brain
- the potential that cannabinoid therapies, as “metabolic regulators“, may increase body weight in those with low weights, but have no impact on or reduce body weight in those with normal or high weights
Given the highly favorable safety profile of whole-plant cannabis and the increasing amounts of evidence suggesting that stimulation of cannabinoid receptors may help increase appetite (and potentially quality of life), as well as possibly control obesity, increasing research on cannabinoid therapies and improving safe access to whole-plant medical cannabis for eligible patients experiencing cachexia, anorexia, and obesity may prove useful for many.