Causes of decreased appetite

Decreased appetite (anorexia) has many causes spanning physical, psychological, and medication-related categories. Here is a quick overview:

Common causes include: infections, cancer, chronic diseases (kidney/liver/heart failure), medications (chemotherapy, antibiotics, opioids), depression, anxiety, thyroid disorders, and normal aging.

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I now have comprehensive textbook data from Harrison's Principles of Internal Medicine (22nd Ed, 2025) and other authoritative sources. Here is a thorough answer:

Causes of Decreased Appetite (Anorexia)

Decreased appetite - clinically called anorexia (distinct from anorexia nervosa) - is a reduction in the desire to eat. It is one of the four major manifestations of unintentional weight loss, along with sarcopenia, cachexia, and dehydration. Most causes fall into four broad categories.

1. Malignant Neoplasms

Cancer is among the most important causes to exclude. The most common malignancies causing anorexia and weight loss are:

Gastrointestinal cancers (stomach, colon, hepatobiliary)
Lung cancer
Hematologic malignancies (lymphoma, leukemia)
Breast, genitourinary, ovarian, and prostate cancers

Half of all cancer patients lose body weight; cachexia (combining anorexia, weight loss, and muscle wasting) directly causes up to 20% of cancer deaths. When malignancy presents primarily as weight loss and anorexia, the prognosis is generally poor. - Harrison's Principles of Internal Medicine, 22E

2. Chronic Inflammatory and Infectious Diseases

Infections: tuberculosis, HIV/AIDS, subacute bacterial endocarditis, chronic fungal infections
Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
Chronic pancreatitis
Cardiac disorders: heart failure, chronic ischemia
Pulmonary disease: COPD, chronic respiratory failure
Renal failure (CKD/ESRD): Uremic anorexia is driven by acidosis, elevated inflammatory cytokines (TNF, interleukins), and elevated leptin levels from adipose tissue acting on hypothalamic appetite centers. There is a characteristic disproportionate reduction in protein intake. - Brenner and Rector's The Kidney
Liver disease: cirrhosis, hepatitis

3. Metabolic and Endocrine Disorders

Condition	Mechanism
Hyperthyroidism	Increased catabolism, altered appetite regulation
Adrenal insufficiency (including ACTH deficiency)	Hypocortisolism causes fatigue, weakness, and anorexia
Diabetes mellitus	Gastroparesis, metabolic derangement
Pheochromocytoma	Catecholamine excess
Hypothyroidism	Can cause anorexia in some patients

Neuroanatomy through Clinical Cases, 3rd Ed; Harrison's 22E

4. Psychiatric and Neurological Disorders

Depression: one of the most common causes of appetite loss overall - Kaplan & Sadock's Comprehensive Textbook of Psychiatry
Anxiety disorders
Anorexia nervosa / bulimia: eating disorder diagnoses requiring exclusion of organic causes
Dementia (Alzheimer's, vascular): impairs recognition of hunger and ability to self-feed
Delirium
Stroke: can impair swallowing (dysphagia) and appetite signaling
Parkinson's disease: dysphagia, dysautonomia, depression
Neuromuscular disorders

5. Medications

This is particularly common in elderly patients taking five or more drugs. - Harrison's 22E

Drug Class	Examples
Sedatives / opioids	Morphine, benzodiazepines
Antibiotics	Metronidazole, macrolides
NSAIDs	Ibuprofen, naproxen
Antidepressants	SSRIs (fluoxetine, sertraline)
Antidiabetics	Metformin, GLP-1 agonists
Dopaminergics	Levodopa
ACE inhibitors	Enalapril, lisinopril
Chemotherapy agents	Most cytotoxics
Cholinesterase inhibitors	Donepezil, rivastigmine

6. Gastrointestinal Disorders

Peptic ulcer disease
Atrophic gastritis / pernicious anemia
Celiac disease
Dysmotility syndromes (gastroparesis)
Intestinal obstruction or constipation (causing early satiety/sitophobia)
Oral/dental problems: caries, abscess, xerostomia, poorly fitting dentures, inability to chew

7. Substance Use

Alcohol abuse: causes poor appetite, impaired intake, and malabsorption - Yamada's Textbook of Gastroenterology, 7E
Cocaine and amphetamines: directly suppress appetite via central stimulant effects - Kaplan and Sadock's Synopsis of Psychiatry
Withdrawal from alcohol or other substances

8. Age-Related and Social Factors

In elderly patients, multiple overlapping factors reduce appetite:

Declining chemosensory function (smell and taste)
Reduced chewing efficiency and dental problems
Slowed gastric emptying
Reduced physical activity and lean body mass
Elevated cholecystokinin (prolonged satiety)
Poverty and food insecurity - up to 30-50% of nursing home patients have inadequate food intake
Social isolation and lack of meal assistance
Harrison's 22E

9. Other Causes

Sleep deprivation: chronic sleep loss impairs glucose tolerance and appetite regulation
Sitophobia: fear of eating due to pain (seen in mesenteric ischemia, peptic ulcer disease)
Hypothalamic lesions: the lateral hypothalamus contains feeding centers; destruction leads to profound anorexia
Pregnancy (first trimester nausea)
Post-surgical states

Key Takeaway

The mnemonic "CAMPSITE" can help organize causes:

Cancer
Aging / social
Metabolic/endocrine
Psychiatric
Substance use
Infectious/inflammatory
Treatment (medications)
Enteric (GI) disease

A basic workup includes CBC, CMP, liver/renal function, thyroid function, CRP/ESR, chest X-ray, abdominal ultrasound, and age-appropriate cancer screening. - Harrison's Principles of Internal Medicine, 22E

Can hiv transmitted through saliva

No, HIV is not transmitted through saliva under normal circumstances. Saliva contains very low concentrations of HIV and also contains proteins (like secretory leukocyte protease inhibitor) that inhibit HIV. Casual contact like kissing, sharing utensils, or coughing does not transmit HIV.

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I have all I need from the textbooks. Here is a thorough, evidence-based answer:

Can HIV Be Transmitted Through Saliva?

The Short Answer: No - Under Normal Circumstances

HIV cannot be transmitted through saliva in everyday situations. This is one of the most well-established facts in HIV medicine, confirmed across multiple authoritative textbooks.

Why HIV Is Found in Saliva But Does NOT Transmit

HIV can be isolated from the saliva of a small proportion of infected individuals, but only typically at very low titers (concentrations). Despite this, no convincing evidence exists that saliva can transmit HIV - through kissing, sharing food/utensils, or occupational exposures to healthcare workers. - Harrison's Principles of Internal Medicine, 22E (2025)

The reason comes down to multiple protective factors in saliva:

1. HIV-Specific Antibodies

Saliva contains HIV-specific immunoglobulins of IgA, IgG, and IgM isotypes in infected individuals. These antibodies neutralize the virus within the oral cavity.

2. Large Glycoproteins

Substances like mucins and thrombospondin-1 physically sequester HIV into aggregates, facilitating clearance by the host before the virus can infect any cells.

3. Secretory Leukocyte Protease Inhibitor (SLPI)

This is the best-studied protective factor. SLPI is found in saliva at concentrations sufficient to block HIV infection in cell culture systems. It works by targeting host cell receptors rather than the virus itself. Higher salivary SLPI levels in breastfed infants were associated with a decreased risk of HIV transmission through breast milk. - Harrison's 22E

4. Submandibular Saliva - Mechanical Disruption

Submandibular saliva appears to reduce HIV infectivity by stripping the gp120 envelope protein from the surface of virions. It can also cause lysis of HIV-infected cells due to the hypotonicity of oral secretions. - Harrison's 22E

What Fluids DO Transmit HIV?

Transmits HIV	Does NOT Transmit HIV
Blood and blood products	Saliva
Semen	Sweat
Vaginal secretions	Tears
Breast milk	Urine
Transplacental (mother to child)	Feces
	Respiratory secretions

Tintinalli's Emergency Medicine; Sherris & Ryan's Medical Microbiology, 8th Ed

"HIV exists in saliva, urine, CSF, pus, brain, tears, alveolar fluid, synovial fluid, and amniotic fluid. Transmission of HIV occurs through semen, vaginal secretions, blood or blood products, and breast milk." - Tintinalli's Emergency Medicine

"HIV has been isolated from many organs and tissues including bone, blood, semen, vaginal secretions, and breast milk, which have been implicated in HIV transmission, but not saliva." - Campbell's Operative Orthopaedics, 15th Ed (2026)

The One Exception: Human Bites

There are a small number of case reports of HIV transmission by human bites. This is because a bite wound involves direct inoculation of saliva into broken skin or a puncture wound, and the biter's saliva may be contaminated with blood from bleeding gums. Even so, this is extremely rare and involves blood contact, not saliva acting as the transmission vehicle per se. - Rosen's Emergency Medicine

Casual Contact - Completely Safe

The following carry zero risk of HIV transmission:

Kissing (including deep/French kissing)
Sharing food, drinks, or utensils
Coughing or sneezing
Hugging or shaking hands
Using the same toilet or pool

"Transmission of HIV infection does not occur with casual contact." - Tintinalli's Emergency Medicine

Bottom Line

Saliva contains HIV at very low levels AND contains multiple active antiviral defense mechanisms (SLPI, IgA/IgG/IgM antibodies, mucins, submandibular factors) that collectively neutralize the virus. You cannot get HIV from kissing, sharing food, coughing, or any form of casual contact involving saliva.

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