question: Why do stimulants (Coffee, adderall, cocaine, etc.) cause a loss of appetite?
comment: Because they activate the part of the brain that wants to hunt. When you hunt you shouldn't feel hungry or you're distracted so the appetite is suppressed.
passages: Certain drugs may increase appetite either as their primary effect or as a side effect. Antidepressants, such as mirtazapine or amitriptyline, and antipsychotics, particularly chlorpromazine and haloperidol, as well as tetrahydrocannabinol (found in cannabis), all present an increase in appetite as a side effect. In states where it is approved, medicinal cannabis may be prescribed for severe appetite loss, such as that caused by cancer, AIDS, or severe levels of persistent anxiety. Other drugs or supplements which may increase appetite include antihistamines (such as diphenhydramine, promethazine or cyproheptadine), and B vitamin supplements (such as vitamin B12 and vitamin B-complex).
   BULLET::::- Interference with the body's ability to absorb specific nutrients in food. For example, Orlistat (also known as Xenical and Alli) blocks fat breakdown and thereby prevents fat absorption. The OTC fiber supplements glucomannan and guar gum have been used for the purpose of inhibiting digestion and lowering caloric absorption
  
  Anorectics are primarily intended to suppress the appetite, but most of the medications in this class also act as stimulants (e.g., amphetamine), and patients have abused medications "off label" to suppress appetite (e.g. digoxin).
  
  Section::::History.
   Changes in appetite or weight are common among antidepressants, but largely drug-dependent and are related to which neurotransmitters they affect. Mirtazapine and paroxetine, for example, have the effect of weight gain and/or increased appetite, while others (such as bupropion and venlafaxine) achieve the opposite effect.
  
  The antihistaminic properties of certain TCA- and TeCA-class antidepressants have been shown to contribute to the common side-effects of increased appetite and weight gain associated with these classes of medication.
  
  Section::::Adverse effects.:Discontinuation syndrome.
   It is quite clear through research, and various studies that overeating causes addictive behaviors. 
  
  In some instances, overeating has been linked to the use of medications known as dopamine agonists, such as pramipexole.
  
  Section::::See also.
  
  BULLET::::- Compulsive overeating
  
  BULLET::::- Counterregulatory eating
  
  BULLET::::- Behavioral addiction
  
  BULLET::::- Binge eating
  
  BULLET::::- Binge eating disorder
  
  BULLET::::- Food drunk
  
  BULLET::::- Gluttony
  
  BULLET::::- Inflammation#Systemic inflammation and overeating
  
  BULLET::::- "" (book)
  
  BULLET::::- Polyphagia
  
  BULLET::::- Fasting
  
  Section::::References.
  
  BULLET::::- Kessler, David A. The End of Overeating: Taking Control of the Insatiable American Appetite (2009)
   Given the epidemic proportions of obesity in the Western world and the fact that it is increasing rapidly in some poorer countries, observers expect developments in this area to snowball in the near future.
  
  Section::::Pharmacology.:Stimulation.
  
  Weight loss or loss of appetite ("cachexia") is an effect of some diseases, and a side effect of some prescription drugs. Three agents are approved for appetite stimulation in the United States: megestrol - a progesterone available as an oral tablet, oxandrolone - an oral anabolic steroid, and dronabinol - a cannabinoid available in an oral capsule.
   BULLET::::- Feeding: a 2012 paper suggested that oxytocin neurons in the para-ventricular hypothalamus in the brain may play a key role in suppressing appetite under normal conditions and that other hypothalamic neurons may trigger eating via inhibition of these oxytocin neurons. This population of oxytocin neurons is absent in Prader-Willi syndrome, a genetic disorder that leads to uncontrollable feeding and obesity, and may play a key role in its pathophysiology.
  
  Section::::Biological function.:Psychological.
   BULLET::::- Norepinephrine is both a neurotransmitter and a hormone; abnormalities in either capacity may affect eating behavior.
  
  BULLET::::- Dopamine: which in addition to being a precursor of norepinephrine and epinephrine is also a neurotransmitter which regulates the rewarding property of food.
   Section::::Indirect manipulation of specific appetite.
  
  Specific appetite can be indirectly induced under experimental circumstances. In one study, normal (sodium-replete) rats exposed to angiotensin II via infusion directly into the brain developed a strong sodium appetite which persisted for months. However, the conclusions of this experiment have been contested. Nicotine implants in rats have been shown to induce a specific appetite for sucrose, even after removal of the implants.
  
  Section::::Specific appetite in humans.
   Medications may affect hedonic eating behavior. Glucagon-like peptide-1 (GLP1) agonists, such as exenatide and liraglutide, which are used for diabetes, may help suppress food reward behavior. Inhibition of dopamine transport within the brain increases dopamine concentrations, which can reduce energy intake. Despite theoretical underpinnings, opiate antagonists as single agents have generally not shown substantial clinical benefit. However, preliminary data has suggested synergistic effects with concurrent targeted therapy of opiate receptors and either dopamine or cannabinoid receptors.
   An increase in dopamine in the caudate and putamen have been found in binge eaters, and studies have found a decrease in a particular serotonin transporter (5-HT) in binge eaters compared to controls. Both the caudate nucleus and putamen make up the dorsal striatum and are important as part of the brain's memory system. Dopamine is required to allow these structures to perform properly and thus this is affected in individuals with binge eating disorders, however the exact mechanism is unknown.
   An orexigenic, or appetite stimulant, is a drug, hormone, or compound that increases appetite and may induce hyperphagia. This can be a naturally occurring neuropeptide hormone such as ghrelin, orexin or neuropeptide Y, or a medication which increases hunger and therefore enhances food consumption. Usually appetite enhancement is considered an undesirable side effect of certain drugs as it leads to unwanted weight gain, but sometimes it can be beneficial and a drug may be prescribed solely for this purpose, especially when the patient is suffering from severe appetite loss or muscle wasting due to cystic fibrosis, anorexia, old age, cancer or AIDS. There are several widely used drugs which can cause a boost in appetite, including tricyclic antidepressants (TCAs), tetracyclic antidepressants, natural or synthetic cannabinoids, first-generation antihistamines, most antipsychotics and many steroid hormones.
   BULLET::::- Chemicals that are members of the phenethylamine group. (Individuals with anorexia nervosa may seek them to suppress appetite.)
  
  BULLET::::- Topiramate may cause anorexia as a side effect.
  
  BULLET::::- Other drugs may be used to intentionally cause anorexia in order to help a patient preoperative fasting prior to general anesthesia. It is important to avoid food before surgery to mitigate the risk of pulmonary aspiration, which can be fatal.
  
  Section::::Causes.:Other.
   BULLET::::- Metabolic disorders, particularly urea cycle disorders
  
  BULLET::::- Pancreatitis
  
  BULLET::::- Stomach flu
  
  BULLET::::- Sickness behavior
  
  BULLET::::- Superior mesenteric artery syndrome
  
  BULLET::::- Tuberculosis
  
  BULLET::::- Thalassemia
  
  BULLET::::- Ulcerative colitis
  
  BULLET::::- Zinc deficiency
  
  Section::::Causes.:Drugs.
  
  BULLET::::- Stimulants, such as ephedrine, amphetamine, methamphetamine, MDMA, cathinone, methylphenidate, nicotine, cocaine, caffeine, etc.
  
  BULLET::::- Narcotics, such as heroin, morphine, codeine, hydrocodone, oxycodone, etc.
  
  BULLET::::- Antidepressants can have anorexia as a side effect
  
  BULLET::::- Selective serotonin reuptake inhibitors (SSRI) such as fluoxetine.
  
  BULLET::::- Byetta, a Type II Diabetes drug, will cause moderate nausea and loss of appetite.
  
  BULLET::::- Abrupt cessation of appetite-increasing drugs, such as cannabis and corticosteroids.
   Lorcaserin (Belviq) was approved June 28, 2012 for obesity with other co-morbidities. The average weight loss by study participants was modest, but the most common side effects of the medication are considered benign. It reduces appetite by activating a type of serotonin receptor known as the 5-HT receptor in a region of the brain called the hypothalamus, which is known to control appetite.
  
  Section::::Medication.:Sibutramine.
   BULLET::::- counteracting the effects of anandamide, another potent hunger promoter that binds to the same receptors as THC
  
  BULLET::::- In the medial hypothalamus, leptin stimulates satiety by
  
  BULLET::::- promoting the synthesis of α-MSH, a hunger suppressant
  
  Thus, a lesion in the lateral hypothalamus causes anorexia (due to a lack of hunger signals) and a lesion in the medial hypothalamus causes excessive hunger (due to a lack of satiety signals).
   Used on a short-term basis clinically to treat obesity, some appetite suppressants are also available over-the-counter. Most common natural appetite suppressants are based on "Hoodia", a genus of 13 species in the flowering plant family Apocynaceae, under the subfamily Asclepiadoideae. Several appetite suppressants are based on a mix of natural ingredients, mostly using green tea as its basis, in combination with other plant extracts such as fucoxanthin, found naturally in seaweed. Drugs of this class are frequently stimulants of the phenethylamine family, related to amphetamine (informally known as "speed").
   Lorcaserin is a selective 5-HT receptor agonist, and "in vitro" testing of the drug showed reasonable selectivity for 5-HT over other related targets. 5-HT receptors are located almost exclusively in the brain, and can be found in the choroid plexus, cortex, hippocampus, cerebellum, amygdala, thalamus, and hypothalamus. The activation of 5-HT receptors in the hypothalamus is supposed to activate proopiomelanocortin (POMC) production and consequently promote weight loss through satiety. This hypothesis is supported by clinical trials and other studies. While it is generally thought that 5-HT receptors help to regulate appetite as well as mood, and endocrine secretion, the exact mechanism of appetite regulation is not yet known. Lorcaserin has shown 100x selectivity for 5-HT versus the closely related 5-HT receptor, and 17x selectivity over the 5-HT receptor.
   Rimonabant (Acomplia), another drug, had been withdrawn from the market. It worked via a specific blockade of the endocannabinoid system. It has been developed from the knowledge that cannabis smokers often experience hunger, which is often referred to as "the munchies". It had been approved in Europe for the treatment of obesity but has not received approval in the United States or Canada due to safety concerns. European Medicines Agency in October 2008 recommended the suspension of the sale of rimonabant as the risk seem to be greater than the benefits. Sibutramine (Meridia), which acts in the brain to inhibit deactivation of the neurotransmitters, thereby decreasing appetite was withdrawn from the UK market in January 2010 and United States and Canadian markets in October 2010 due to cardiovascular concerns.
   In the United States orlistat (Xenical) is currently approved by the FDA for long-term use. It reduces intestinal fat absorption by inhibiting pancreatic lipase. Rimonabant (Acomplia), a second medication, works via a specific blockade of the endocannabinoid system. It has been developed from the knowledge that cannabis smokers often experience hunger, which is often referred to as "the munchies". It had been approved in Europe for the treatment of obesity but has not received approval in the United States or Canada due to safety concerns. The European Medicines Agency in October 2008 recommended the suspension of the sale of rimonabant as the risks seem to be greater than the benefits. Sibutramine (Meridia), which acts in the brain to inhibit deactivation of the neurotransmitters, thereby decreasing appetite was withdrawn from the United States and Canadian markets in October 2010 due to cardiovascular concerns.
   Certain medications may cause weight gain or changes in body composition; these include insulin, sulfonylureas, thiazolidinediones, atypical antipsychotics, antidepressants, steroids, certain anticonvulsants (phenytoin and valproate), pizotifen, and some forms of hormonal contraception.
  
  Section::::Causes.:Social determinants.
   BULLET::::- Increase of stimulation, tense body
  
  These effects are related with addiction potential. Excessive salivation is not an effect that is typically reported in humans. It is suggested that methedrone increases salivation via brain systems that primarily regulate autonomic responses.
  
  Compared with mephedrone, methylenedioxypyrovalerone (MDPV) and 4-fluoromethcathinone (4-FMC), methedrone has a relatively slow onset. Thereby increasing the risk; because effects are not immediately shown, this could lead to an accidental overdose. It could also make the drug less popular, because humans tend to favor drugs that cause large, rapid initial increases in locomotor activity.
  
  Section::::Toxicity.:Chronic toxicity.
   Signals arising from the long-term nutrient reservoir of the body may alter the sensitivity of the brain to hunger signals or short-term satiety signals. A peptide, leptin, has profound effects on metabolism and eating. It is secreted by adipose tissue and it increases metabolic rate while decreasing food intake. Its discovery has stimulated interest in finding ways of treating obesity.
  
  Section::::Brain mechanisms.
   Section::::Role in disease.:Pediatric eating problems.
  
  Eating issues such as "picky eating" affects about 25% of children, but among children with development disorders this number may be significantly higher, which in some cases may be related to the sounds, smells, and tastes (sensory processing disorder).
  
  Section::::Pharmacology.
  
  Glycemic index has been thought to effect satiety; however, a study investigating the effect of satiety found that a high-glycemic food, potatoes, reduced appetite more than a low glycemic index food.
  
  Section::::Pharmacology.:Suppression.
   Amphetamines are used as a stimulant to trigger the central nervous system, increasing heart rate and blood pressure while decreasing appetite. Since amphetamines are a stimulant, use of these drugs result in a state that resembles the manic phase of bipolar disorder and also produces similar symptoms, as stated above. 
  
  Section::::Associated conditions.:Attention deficit hyperactivity disorder.
   Complicating matters is that the composition of the food eaten (see "glycemic index") affects intestinal absorption rates. Glucose from some foods is absorbed more (or less) rapidly than the same amount of glucose in other foods. In addition, fats and proteins cause delays in absorption of glucose from carbohydrates eaten at the same time. As well, exercise reduces the need for insulin even when all other factors remain the same, since working muscle has some ability to take up glucose without the help of insulin.
  