No doubt, many of us wouldn’t mind if we had less of an appetite from time to time! However, when decreased appetite comes about as a result of a mental condition or physical illness, it can become a serious issue. Left unmanaged, beyond weight loss, it can lead to serious health problems such as malnutrition, muscle wasting, fever, extreme fatigue, irritability, a rapid heartbeat, general ill feeling, and even potentially, death.
The first line of defense against loss of appetite is to determine what the root cause is and treat the underlying issue. For others, those suffering from conditions such as cancer (and, associated radiation or chemotherapy), AIDS/HIV, and even, anorexia, report that using cannabis has helped them restore their appetite.
It’s not exactly a well-kept secret that “smoking a little kush” causes the “munchies.” Popular media humorously describes characters getting the “munchies” after partaking in cannabis — think “Harold & Kumar Go To Whitecastle.” The non-scientific term “munchies” — which, of course, means ‘the uncontrollable desire to eat (often to excess) after imbibing in cannabis — is a relatively new addition to the popular lexicon. However, the use of marijuana as an appetite stimulant has a long history going back thousands of years. Records found in China dating back to 2700 B.C. provide insights into how cannabis — in the form of tea — was used to stimulate appetite. Similarly, ancient documents reveal Indian practitioners of Ayurvedic medicine also used cannabis as an appetite stimulant.
What Causes A Decreased Appetite?
While conditions like HIV/AIDS, cancer and anorexia can cause a loss of appetite, numerous other issues can also reduce appetite. Some, like stress, soon pass. Other conditions, like anorexia, may require medical attention. Contrary to common belief, in cancer, while sometimes cancer itself causes a loss of appetite — especially stomach, ovaries, colon, or pancreas — more often, it is a result of radiation or chemotherapies. Generally, in any of the conditions that cause a loss of appetite, once treated, appetite returns to normal.
Common Environmental Factors Causing Loss of Appetite
Psychological Causes: Loss of appetite often accompanies feelings of sadness, grief, anxiety or depression.
Bacteria and Viruses: One of the most common causes of diminished appetite is a bacterial or viral infection. For example, a common complaint of flu — along with coughing and drowsiness — is a loss of appetite. Short in duration, appetite quickly resumes to normal after the infection goes away.
Eating Disorders: A predominant symptom among individuals suffering from anorexia nervosa is a decrease in appetite. Underweight, and fearful of gaining weight, sufferers often turn to starving themselves which can lead to malnutrition.
Stress and Anxiety: Loss of appetite often accompanies acute, or persistent stress and anxiety. Even simple boredom cause a loss of appetite.
Drugs or Medications:
A variety of drugs and medications can affect appetite including:
Street Drugs: including cocaine, heroin, and amphetamines.
Prescription Medications: including antibiotics, opioids, and chemotherapy drugs.
Other Medical Conditions
We mentioned HIV/AIDS, cancer, and anorexia, but several other medical conditions can cause a decrease in appetite, including:
Chronic liver disease
Hypothyroidism (underactive thyroid)
The Scientific Basis: Why Does Cannabis Stimulate Appetite?
Affecting nearly every physiological process, the endocannabinoid system (ECS) is one of the body’s most important physiological systems. Remarkably, scientists only recently discovered the ECS (just over two decades ago). The ECS serves as a critical regulatory mechanism in the body's biochemistry and physiology; it is the essential machinery that governs everyday life. Italian Professor Di Marzo, research director at the Institute of Biomolecular Chemistry of the National Research Council, best summarized the endocannabinoid system’s essential functions: "[The ECS helps us] relax, eat, sleep, forget and protect."
No doubt, the ECS plays a crucial role in appetite — including mediating hunger and stimulating appetite. Predictably, manipulating the ECS can result in increasing appetite (or potentially suppressing it).
The endocannabinoid system has two primary cannabinoid receptors responsible for helping modulate a variety of actions:
CB1: Appetite, muscle control, pain, cognition, and reward
CB2: Immune function, cell proliferation, inflammation, and pain
While embarking on research to learn how activation of the CB1 receptor could lead to overeating, scientists from Yale School of Medicine, found what they believe to be the neurological basis for what causes the “munchies” after users consume cannabis.
Researchers determined the effect was driven by the same brain neurons that are responsible for suppressing appetite. Investigators studied experimental mouse models to monitor the brain, selectively manipulating the cellular pathway responsible for mediating the actions of ingested cannabis on the brain.
Published in the Feb 2015 issue of the journal, Nature, lead investigator, Tamas Horvath, a professor of neurobiology and director the Yale Program in Cell Signaling and Neurobiology of Metabolism, reported:
“By observing how the appetite center of the brain responds to marijuana, we were able to see what drives the hunger brought about by cannabis and how that same mechanism that normally turns off feeding becomes a driver of eating.” Horvath further explains that, “It’s like pressing a car’s brakes and accelerating.”
Horvath’s team was surprised evidence suggested: “[T]he neurons we thought were responsible for shutting down eating, were suddenly being activated and promoting hunger, even when you are full. It fools the brain’s central feeding system.” Remarkably, the neurons responsible for stimulating appetite are the same neurons responsible for making humans “feel full.”
While the Yale researchers noted the need for further research to validate their findings, they were impressed by evidence suggesting the potential for medical cannabis to play a major role in treatment plans for those suffering from a wide variety of medical conditions associated with the loss of appetite.
The Research: How Effective Is Cannabis At Treating Appetite Loss?
While science shows us why cannabinoids act as appetite stimulant, it’s well-established among cannabis consumers that one of the key effects of cannabis consumption is an increase in appetite. In 2011, Dr. Donald Abrams, professor of clinical medicine at the University of California, San Francisco and chief of hematology & oncology at San Francisco General Hospital was asked about the accumulating evidence validating what he (and millions of patients have long known) about cannabis as an appetite stimulant: “I don’t think there’s anything startling about the fact that cannabis or cannabinoids increases the appetite. That’s been well known for years.”
While to many, employing whole-plant cannabis as part of a treatment program seems like a “no-brainer,” resistance persists. Misconceptions and divergent opinions over whole-plant cannabis as a treatment option continue, generally attributed to potential side effects, variable chemical composition, and a lack of “gold standard” study trials. Many of these concerns could be allayed with more randomized-controlled trials (RCTs), but federal policy has long impeded research. While the federal government has eased some of the obstacles, it will be years before we’ve accumulated enough evidence to alleviate concerns of the most skeptical in the medical community.
Cancer & HIV/AIDS
Patients afflicted with conditions such as cancer and HIV/AIDS often experience increased demands on their metabolism coupled with a decrease in nutritional intake. These demands can result in decreased appetite followed by weight loss and tissue wasting. Untreated, these complications can lead to death. Synthetic cannabinoid treatments — like Marinol and Cesamet — have been approved to treat symptoms related to these conditions, although patients widely report the prefer botanical cannabis over their synthetic counterparts.
As far back as 1982, the Michigan Department of Health conducted a study of cancer patients who were given cannabis or a pharmaceutical to treat side effects of chemotherapy (namely nausea and lack of appetite). The study reported that 90 percent of the patients who received cannabis chose to continue using it, while just eight of those patients chose to discontinue cannabis in favor of the pharmaceutical. In contrast, 22 of the 23 patients using the pharmaceutical opted to abandon its use for cannabis. Moreover, 71 percent of patients treating with cannabis reported that even after chemotherapy, they didn’t experience vomiting and only had mild nausea.
Many studies indicate that it is common among many HIV and cancer patients to use cannabis to stimulate appetite and weight gain and that it’s for this reason they report as the primary motivating factor driving their choice of cannabis. Likewise, many patients report a preference for inhaled (smoked or vaped) cannabis to synthetic alternatives — like Marinol — because they can self-titrate an effective dose that takes effect immediately. Oral consumption, in contrast, produces a delayed onset of effects and is often much more potent — leaving patients feeling far more “high” than tolerable. Since THC — the primary psychoactive constituent in cannabis — is not water soluble; thus, inhalation which elicits peak effects within two to five minutes is a more efficient method of delivery.
The Washington, D.C.-based, Institute of Medicine in (part of the National Academy of Sciences), a group not known for supporting medical marijuana, published a systematic review of 15 studies in 1999. Among other findings, they acknowledged, “accumulated data indicate a potential therapeutic value for [cannabis] drugs, particularly for symptoms such as pain relief, control of nausea and vomiting, and appetite stimulation.” The report's authors reasoned that the effectiveness and potential benefits of inhaled cannabis (preferably by means other than “smoking”) might outweigh the risks and be appropriate for patients with anorexia associated with HIV/AIDS or cancer.
However, some studies claim cannabis — particularly “smoked” cannabis — pose risks in HIV/AIDS and cancer patients, including hypotension and tachycardia (rapid heartbeat that may be regular or irregular, but disproportionate to the level of exertion). Further, in patients whose immune system may be vulnerable, the risk of being exposed microbes could compromise the body’s immune response and pose significant risks. Although, no patients or physicians have reported adverse interactions with antiretroviral therapies such as indinavir and nelfinavir.
Anorexia, clinically known as anorexia nervosa, disproportionately affects women — particularly at vulnerable ages like adolescence and college. At any given time, at least one to three out of every 100 women in the U.S., while studies estimate that among college women, as many as 10 percent may suffer from a clinically diagnosable eating disorder. An estimated 0.3 percent of men suffer from anorexia nervosa.
Anorexia Nervosa — distinct from anorexia associated with another condition like AIDS/HIV — is generally characterized by body dysmorphia, an irrational fear of gaining weight, and accompanying unhealthy low weight. Other accompanying issues include body-image insecurities and an unhealthy perception of one’s body. Physical effects include a loss of bone density, anemia, heart-rhythm disturbances, and digestive problems. Over a ten-year period, as many as five percent of those with long-term anorexia will die from the condition. Depression (and sometimes suicidal ideation) often accompany anorexia.
Although several lines of evidence from preclinical research on eating disorders provide evidence suggesting the presence of a dysfunctional endocannabinoid system (ECS), human studies have yet to emerge that validate early research. Nor, have human studies conclusively proven cannabis could be an effective treatment for those suffering from anorexia nervosa. From the little data we have, the evidence is often contradictory, but could be explained by confounding factors such as chronic versus acute use, use of other drugs (e.g. stimulants), or potential competition between food and drugs for the same reward pathways in the brain.
One report published in Biological Psychiatry suggests endocannabinoid functional deficits may be partly responsible for anorexia nervosa and bulimia. In contrast to healthy subjects, they found consistent alterations in how ligands bind to CB1 receptors in the brains of women who had anorexia nervosa indicating the a strong likelihood of “a compensatory process engaged by deficits in endocannabinoid levels or reduced CB1 receptor function."
Researchers concluded by stating the obvious: "The role of endocannabinoids in appetite control is clearly important.” However, investigator Dr. John Krystal, editor of Biological Psychiatry, noted that their research identified new data points suggesting an important link between the endocannabinoid system and eating disorders. The researchers called for additional research to establish whether anorexia nervosa caused the observed changes or if the neurochemical alterations existed before developing the eating disorder, and may serve as risk factors.
Given the fact, as the authors noted, because so few effective treatments to treat eating disorders exist, research into novel therapies targeting the endocannabinoid system would be clearly worthwhile.
The researchers’ conclusions, led by Dr. Koen Van Laere, the study's lead author stand in stark contrast to a much earlier study from 2002, that while providing evidence that cannabis could be useful for Alzheimer’s patients experiencing difficulty gaining weight, in patients suffering anorexia nervosa stood to gain little benefit from cannabis. They found no statistically significant effect they could attribute to cannabinoids leading the researching to speculate the reason being the “underlying pathological mechanism is not the loss of appetite,” but rather the lack of appetite stemmed from a psychiatric condition that produced physical symptoms — not eating — cannabis fails to treat the underlying cause.
Nonetheless, others argue that cannabis is a far more humane method of treating anorexia sufferers than forcing food down a feeding tube. Given how the latter method could only compound self-esteem issues patients are already suffering, to consider cannabis as an alternative certainly seems reasonable, if not prudent. Moreover, cannabis may be able to ease some of their stress and anxiety which contribute to the disorder. In turn, allowing them to be more amenable to accepting other forms of treatment from counselors or other professionals.
Moreover, there are some anecdotal reports from sufferers who claim cannabis helped them overcome false individual perceptions they had of themselves as being overweight — body dysmorphia — when in fact, they were malnourished and underweight. Likewise, patients have reported that cannabis consumption helps them promote healthy introspection, affording them the ability to possibly gain insight into some of the underlying motivations were of their disorder.
When it comes to treating anorexia nervosa, the jury may still be out and science needs to catch up to provide more conclusive results. However, given the plausibility that cannabis could lead to a decrease in depression and anxiety symptoms, distorted perceptions of self, and an increase in caloric intake — clearly further research is warranted to determine if cannabis could provide a viable therapeutic pathway to treat anorexia
Ultimately, the causes of decreased appetite are diverse and complex. If related to acute illness — like an infection — or temporary stress, no treatment is likely needed. Often, simple things like cooking favorite meals, going out to a restaurant, or eating with friends and family can help regain appetite. Likewise, starting with light exercise or focusing on eating light snacks throughout the day (or one big meal per day) may help.