Cannabis is infamous for causing ravenous hunger. This is so well-known that it is an integral aspect of the mainstream media’s “stoner stereotype”—the red-eyed, indolent (and usually male) twenty-something who plays video games all day and is never without a bag of Cheetos. Here, we attempt to explain this complex phenomenon.
How the brain produces sensations of hunger
Cannabis is infamous for causing users to feel intensely hungry.
When hunger is experienced, it is in response to a complex system of nerve signals between the gastrointestinal (GI) tract and the brain. The vagus nerves of the peripheral nervous system that surrounds the GI tract sense the levels of macronutrients present in the stomach and bowel, and send signals to the brain if nutrients are low. The specific area of the brain responsible for causing sensations of hunger is the lateral hypothalamus, which is often simply known as the “hunger centre”.
The vagus nerves themselves are stimulated by a neuropeptide known as ghrelin, which is produced in the GI tract when the stomach is empty. Presence of ghrelin stimulates the ghrelin receptors of the vagus nerves, which send signals to the lateral hypothalamus, which in turn creates the motivational state of hunger—as well as increasing gastric acid secretions and intestinal mobility in anticipation of food being consumed.
How THC tricks the body into wanting more food
The metabolic processes at work when hunger is stimulated by use of cannabis are not fully understood, but it is known that an enzyme—AMP-activated protein kinase (AMPK), produced in the hypothalamus—has a fundamental role to play. The enzyme is crucial to the metabolic processes that regulate energy homeostasis (energy balance) in the body, and is produced in response to ghrelin-induced stimulation of the GHS-R1a receptors of the vagus nerves.
Various studies have shown that THC can effectively do the job of ghrelin by activating the GHS-R1a receptors and directly stimulating the brain to produce AMPK and resultant sensations of hunger. Thus, even if the stomach is not empty, use of cannabis can cause powerful sensations of hunger. Further studies have demonstrated that the cannabinoid receptors themselves also have a role to play.
A 2008 study showed that the CB₁-receptor assists in the regulation of ghrelin-induced appetite stimulation—in mice that had been genetically modified to lack CB₁-receptors, ghrelin did not cause an orexigenic (appetite-stimulating) effect; as well as this, the effect of ghrelin on levels of AMPK in the hypothalamus was inhibited both in CB₁-knockout mice and in wild-type mice administered with rimonabant, an inverse agonist of the CB₁-receptors. The presence of ghrelin was also found to increase endocannabinoid levels in the hypothalamus of wild-type mice, an effect that was inhibited by administering rimonabant. This effect of ghrelin was not seen in CB₁-knockout mice.
Ghrelin, cannabinoids and metabolic function
Cannabis can also cause a drop in blood sugar which can cause temporary weakness and dizziness (© Mandajuice)
An interesting and little-known effect of the interaction between cannabinoids, ghrelin and AMPK is that of ischemic heart protection. Cannabinoids have a range of effects on heart function, and in a very small subset of predisposed individuals ingestion of exogenous cannabinoids may even trigger acute myocardial infarction (heart attack). However, outside of this small subset, it appears that the effects of increasing cannabinoid levels in the heart have several beneficial effects.
Cannabis can also cause a drop in blood sugar which can cause temporary weakness and dizziness.
Both ghrelin and cannabinoids increase AMPK activity in the heart as well as in the hypothalamus; the effect of cannabinoids on AMPK activity is thought to reduce infarct size (area of tissue necrosis) in the myocardium following a heart attack, limiting damage to the heart and circulatory system, as well as provide a generally positive effect on blood flow in cases of ischemia.
Another interesting point is that as well as increasing AMPK activity in the heart, ghrelin and cannabinoids both exhibited the ability to inhibit its activity in the liver and adipose (fatty) tissue, which has a range of effects on expression of glucose and insulin in the blood. This is thought to play an important part in maintenance of weight and body fat in cannabis users, who have been shown on in several studies to possess smaller waist circumferences than non-users.
Thus, even if succumbing to the temptation of the munchies, most cannabis users can feel safe in the knowledge that they are providing their bodies with a significant level of protection against possible negative repercussions of over-indulging on unhealthy food, both by protecting the heart and limiting the deposition of body fat.
Cannabis, blood sugar, and hunger
A sugary drink or snack is all that is needed to return blood sugar to normal levels.
A sugary drink or snack is all that is needed to return blood sugar to normal levels (© Chef Cooke)
Cannabis use is well-known to have an effect on blood sugar levels; for inexperienced users, this effect can be dramatic, and can result in a drop in blood sugar levels that may lead to weakness, sickness or even temporary unconsciousness. It may also increase feelings of hunger acutely, as the body reacts both to the cannabis’ own appetite-stimulating effects and to the effect of low blood sugar itself.
If symptoms of low blood sugar are experienced immediately following consumption of cannabis, providing a sugary drink or snack is a quick and effective remedy. Even if loss of consciousness occurs, this typically lasts just a few seconds, and unless injury has been sustained (such as by falling), the individual should experience no long-term ill effects. The affected individual should be helped into a sitting position and provided with a sugary drink or snack, and should remain seated until any feelings of shakiness or dizziness have passed. Providing more substantial food within an hour of such episodes will also help to maintain blood sugar.
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