What are the possible causes of anorexia and dysgeusia?

Causes of Loss of Appetite and Loss of Taste

Loss of appetite (anorexia) and loss of taste (dysgeusia) share multiple overlapping causes, with the most critical being chronic medical diseases, polypharmacy, cancer and its treatments, oral/dental problems, depression, and social isolation—all of which require systematic evaluation to identify reversible causes that directly impact mortality and quality of life. 1

Primary Causes to Evaluate

1. Medications (Polypharmacy)

Numerous drugs cause dry mouth and alter taste function, resulting in poor perception of otherwise palatable foods. 1 This is particularly common in elderly patients and represents one of the most reversible causes. Medications can also cause:

• Diarrhea, nausea, and abdominal discomfort directly linked to poor food intake
• Drug-nutrient interactions affecting absorption and metabolism 1

Physicians should make every effort to reduce the number of medications, as this improves both adherence and nutritional outcomes. 1

2. Chronic Medical Diseases

Diseases associated with the following symptoms commonly cause anorexia 1:

• Fatigue
• Loss of coordination of body functions
• Restriction of mobility
• Pain
• Nausea
• Acute malaise

3. Cancer and Cancer Treatments

Cancer-related anorexia and dysgeusia are driven by proinflammatory cytokines and tumor-derived factors that alter CNS appetite signals. 2 Specific mechanisms include:

• Altered hypothalamic control of appetite and satiety
• Physical limitations: mouth ulcers, GI obstruction 2
• Treatment effects: Chemotherapy and radiotherapy cause nausea, vomiting, mucositis, dysgeusia, and xerostomia 3, 4
• Systemic inflammation causing metabolic derangements that cannot be reversed by nutrition alone 5

Reversible causes such as oropharyngeal candidiasis and depression should be addressed first. 6

4. Oral and Dental Problems

Problems may be due to 1:

• Poor dental care
• Poorly fitted dentures
• Gingivitis
• Dry mouth (xerostomia)
• Poor oral hygiene

Many of these problems are potentially reversible and should be screened for and corrected if present. 1

5. Age-Related Changes

Age-related reduction in appetite is usually mild but is associated with 1:

• Reduced taste and smell senses
• Decline in metabolism and physical activity
• Social isolation
• Physical disability
• Inability to shop or prepare tasty meals

6. Depression and Psychological Factors

Depression can lead to poor appetite and undernutrition, particularly in the elderly. 1 Social isolation and eating alone are major contributors to eating poorly. 1

7. Nutritional Deficiencies

Zinc, copper, and other micronutrient deficiencies can cause hypogeusia (diminished taste), with bitter and sour taste most severely affected. 7 However, plasma zinc levels do not always correlate with taste recognition scores. 7

Clinical Approach

Immediate Assessment

1. Review all medications for those causing dry mouth, altered taste, nausea, or GI symptoms
2. Screen for reversible causes:
   • Oropharyngeal candidiasis (especially with grade ≥2 symptoms)
   • Depression
   • Dental/oral problems
3. Evaluate for underlying disease: cancer, infection, inflammatory conditions
4. Assess nutritional status: weight loss, BMI, muscle mass, performance status

Common Pitfalls to Avoid

• Overlooking medication side effects as the primary cause—this is often the most reversible etiology
• Failing to screen for oral candidiasis in patients with cancer or immunosuppression
• Missing depression as a contributing factor, particularly in elderly or isolated patients
• Not recognizing that cancer-related anorexia requires multimodal treatment beyond nutrition alone (addressing inflammation, symptoms, psychological distress)

When to Suspect Specific Etiologies

• Recent medication changes: Consider drug-induced dysgeusia/anorexia
• Cancer diagnosis or treatment: Expect cytokine-mediated anorexia and treatment-related dysgeusia 3
• Elderly with polypharmacy: High likelihood of medication-related causes 1
• Acute onset with fever: Consider infection (including COVID-19, which causes anosmia and dysgeusia) 8
• Chronic progressive symptoms: Evaluate for malignancy, chronic inflammatory conditions

The key principle is identifying and treating reversible causes first—particularly medications, oral problems, and depression—as these interventions can significantly improve quality of life and nutritional outcomes. 1, 6