There is a long-held understanding amongst the public that cannabis increases appetite – colloquially and notoriously labelled the munchies. With the increasing acceptance of medicinal cannabis as a viable treatment option globally, modern science is harnessing the effect of the munchies for medicinal uses.
In extreme cases, prolonged lack of appetite can lead to individuals “wasting away”, known as cachexia or wasting syndrome, in relation to oncology patients this is known as CACS – cancer-related anorexia-cachexia syndrome. Another condition where appetite and cachexia are often encountered is HIV and AIDS patients.
Hunger and appetite are often lumped together, yet they are in fact two different experiences. Hunger is essential to human survival and describes the physiological need to eat, whereas appetite is generally regarded as the desire to eat and food preferences. The need to eat to maintain energy and nutritional status are so integral they are controlled by a very important part of the brain, primarily the hypothalamus.
Despite its importance, hunger can be suppressed, and in certain diseases such as cancer and other chronic physical or mental illnesses, long term loss of appetite can lead to dysregulation in the appetite and hunger hormones that moderate food intake and desire to eat.
Our primary hormones that regulate appetite include; ghrelin, which stimulates appetite; PYY, that moderates fullness or satiety; and leptin, which acts to inhibit hunger and regulates energy balance in the body. After food is ingested insulin modulates cellular uptake of glucose (the primary source of energy for cells) and the presence of glucose inhibits the release of ghrelin, telling the brain we need not eat any more.
In short, we have a stimulator, a moderator and an inhibitor that act as key instruments in a larger orchestra that controls appetite and hunger. So can cannabinoids directly affect these hormones and our appetite?
THC is the cannabinoid traditionally associated with the euphoric and appetite-stimulating aspects of cannabis. Far from its stereotypical munchies connotation, THC-based medicinal cannabis and synthetic THC formulations are now being used to stimulate appetite in patients in whom a lack of appetite or weight loss are side effects of medications or the disease.
There are two main circumstances where most of the research into THC and appetite has been channelled: cancer and HIV/AIDs. Several investigations from the 1990s showed the benefits of THC or synthetic THC in terms of positive weight management during advanced cancer. In the example of HIV, when compared to controls -who lost weight during the study period- those treated with THC maintained or gained body weight. This and follow up studies also recorded positive impacts not only in appetite and weight but also in relation to mood and sleep when treated with cannabinoid medicines.
A more recent assessment of the actual changes in appetite hormones in HIV patients was conducted as a substudy of research regarding THC and chronic pain. When treated with THC, blood tests showed a 42% increase in the appetite-stimulating hormone, ghrelin, compared to a 12% increase in the placebo group. Additionally, a decrease of 14% in PYY – the satiety hormone – was observed.
Another human study on healthy individuals released in 2020 compared changes in hormones when administered via oral (edible), smoked or vaporised medicinal cannabis to a placebo. Notable differences were observed between the routes of the medical cannabis delivery, providing yet more confirmation of changes in appetite mediating hormones initiated by THC, supporting its ongoing clinical research and current application in patients.
As of yet, there is no evidence to suggest that CBD has a direct impact on appetite or hunger hormones. However, CBD oil is known for its wide-ranging effects on several different body systems and may have positive, indirect effects on appetite.
Nausea and vomiting, experienced together or separately, can be a huge impediment to a healthy appetite. Research into CBD oil’s action on nausea and vomiting is limited in humans, yet animal research shows that at certain doses CBD reduces retching and can have anti-emetic actions (vomiting reducing effect). This is believed to be due to the cannabinoid acting on the region of the brain that controls the vomit-reflex.
This information may seem contrary to the common side effect of CBD oil, being nausea. However, it is known that CBD (and other cannabinoids) can act in a biphasic manner, where low doses may inhibit nausea and vomiting, while higher doses promote it.
CBD’s effect on mood and anxiety may also have an indirect effect on appetite. Anxiety and other mood disorders often lead to sympathetic nervous system (SNS) dominance. The SNS portion of our nervous system is the one that controls ‘fight and flight’, a part of being in this flight/fight survival mode is the downregulation of digestion. Once upon a time, that would have helped humans running from predators, yet nowadays our bodies react in the same way to non-life-threatening events as they would to a tiger on our tails.
CBD oil medical cannabis promotes a shift to the parasympathetic nervous system, the ‘rest and digest’ aspect of the nervous system. In reducing SNS dominance CBD holds promise to create a more conducive mental and physiological environment for appetite and digestion.
As an anti-inflammatory there is a potential CBD may reduce discomfort and inflammation in the digestive tract that could also be a factor in individuals reduced desire to eat.
For patients with Irritable Bowel Diseases (IBD), like ulcerative colitis or Crohns, a maelstrom of symptoms like diarrhea, constipation, abdominal pain, plus pharmaceutical drugs can result in decreased or entirely absent appetite and unintended weight loss. In such cases, medical cannabis can have anti-inflammatory action, soothing the digestive system, as well as stimulating appetite. An Israeli study showed significant changes in a number of measures including physical pain and positive changes in body weight measured as BMI in IBD patients. This was observed especially in those who were severely underweight.
Small studies of advanced cancer patients with cancer-related anorexia cachexia syndrome (CACS) who are treated with medical cannabis, have not only shown meaningful increases in appetite and body weight, but also enhanced sensory experience around eating, desire and enjoyment in eating.
Medical cannabis formulations including THC and CBD may offer less side effects (intoxication, dry mouth, anxiety) than isolated cannabinoid medicines. While research has touched on the potential impact of the Entourage Effect in terms of appetite, studies on both the synergistic effects of cannabinoids as well as appropriate dosing are lacking.
During deleterious treatments like chemotherapy or radiation, nausea and vomiting can negatively impact food intake and nutrient absorption. Energy, nutrients and antioxidants from the diet that are essential in maintaining healthy body composition, metabolic processes and overall vitality are often in short supply whilst undergoing treatment and compound symptoms.
By reducing nausea and/or vomiting with medical cannabis for patients who are having trouble with appetite or keeping food down, cannabinoids medicines can offer an opportunity to improve their nutrient and energy consumption, and in doing so potentially positively impact quality of life.
Early preclinical animal studies have shown positive benefits on appetite and weight gain with some of the minor cannabinoids, other than the two most often discussed, CBD and THC. For example, CBG, known as the ‘mother’ or ‘stemcell’ cannabinoid from which all others are derived, has been shown to reduce chemotherapy-induced weight loss and increase food intake in animal models.
Delta-8-THC is a minor cannabinoid that has similar structure and action to the major cannabinoid delta-9-THC, with less psychoactivity or intoxicating effects. Professor Raphael Mechoulam, the grandfather of modern medical cannabis, conducted a small study on young children with blood cancers and found delta-8-THC completely prevented vomiting episodes surrounding treatment. Again in terms of encouraging appetite and engagement with food, reducing nausea and vomiting can play a big role.
Many have not heard of this body system which plays an essential role in everything from immune responses to brain function and even digestion. The Endocannabinoid System (ECS) is made up of receptors and endocannabinoids (cannabis-like compounds made within your body). Cannabinoids from plant or synthetic sources, as well as endocannabinoids interact with these receptors and cause physiological changes.
Anandamide is the primary endocannabinoid that is involved with appetite and hunger. Interaction between endocannabinoids and receptors in the gastrointestinal tract modulate the messages sent from the hypothalamus to the brain which triggers the cascade of appetite hormones.
So, by using specific medical cannabis formulations or providing other compounds that activate aspects of the ECS there is a potential of utilising this little known, but hugely important body system to promote appetite.
It is important for medical professionals to assess patients as unique individuals, observing their specific combination of symptoms and disease manifestation to discern the appropriate medical cannabis dose and treatment regime. This kind of personalised medicine promotes better patient outcomes and avoids variables that can decrease the effectiveness of medicinal cannabis treatments when administered in a one-size-fits-all approach.
Although some research in the past decade has shown mixed results regarding medical cannabis and appetite, there are enough positive indications of effectiveness to warrant further research. Research in the coming years should provide more details on appropriate doses and cannabinoid combinations to investigate if it is a worthwhile option compared to conventional treatments.
Whilst researchers continue to focus their efforts into new ways of combating COVID-19, a number of researchers are looking into whether cannabis or cannabis derived CBD (cannabidiol) or THC (tetrahydrocannabinol) might offer support for those suffering from severe forms of this infection.