Causes of decreased appetite
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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
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