What causes poor appetite?

Causes of Poor Appetite

Poor appetite is primarily caused by physiological disruptions, psychological factors, and disease-related inflammation, with cancer, diabetes, infections, medications, and mental health conditions being the most significant contributors.

Physiological Causes

Disease-Related Inflammation

• Cancer-related factors: Cancer causes poor appetite through:

  • Tumor-derived inflammatory cytokines (IL-1, IL-6, TNF-α) that directly affect the central nervous system's appetite control centers 1
  • Systemic inflammation altering metabolism of carbohydrates, fats, and proteins 1
  • Tumor hypoxia leading to metabolic alterations 1

• Infection-related anorexia:

  • Sickness-associated anorexia is triggered by inflammatory cytokines that induce immune responses 1
  • This is likely an evolved strategy to protect the host during infection 1
  • Metabolic adaptations during infection may benefit from reduced caloric intake in certain circumstances 1

• Diabetes-related factors:

  • Metabolic perturbations can disrupt hunger and satiety cues 1
  • Physiologic disruption rather than psychological origin may drive apparent disordered eating 1
  • Incretin therapies affect appetite and reward circuitries, suggesting underlying metabolic mechanisms 1

Physical Limitations and Treatment Effects

• Cancer treatment side effects:

  • Pain, fatigue, dry mouth, mouth ulcers, difficulty chewing
  • Dysphagia, abdominal pain, nausea, vomiting
  • Intestinal blockage, constipation, diarrhea 1

• Medication side effects:

  • Antidepressants like fluoxetine can cause significant weight loss and anorexia (decreased appetite) 2
  • In clinical trials for major depressive disorder, 11% of patients on fluoxetine reported anorexia versus 2% on placebo 2

Psychological Factors

Mental Health Conditions

• Depression and anxiety:

  • Poor mood is independently associated with reduced appetite 3
  • Cultural expressions of depression may include somatic symptoms that affect appetite 1

• Stress:

  • Chronic life stress alters overall food intake in two ways - under- or overeating 4
  • Stress severity influences whether someone under-eats or over-eats 4
  • Stress-induced eating may contribute to obesity development in some individuals 4

Behavioral Factors

• Physical activity levels:
  • Lower habitual physical activity is associated with poorer appetite, particularly in hospitalized older adults 3
  • This relationship remains significant even after controlling for other factors 3

Special Populations

Elderly Patients

• Anorexia of aging:
  • Particularly problematic in hospitalized older adults 3
  • Associated with development of malnutrition, frailty, and sarcopenia 3
  • 43% prevalence of poor appetite in hospitalized older adults 3

Patients with Chronic Conditions

• Peritoneal dialysis patients:
  • Abdominal discomfort from the procedure
  • Absorption of osmotic agents
  • Increased peritoneal solute transport rate linked to protein-energy wasting
  • Inflammation contributing to malnutrition-inflammation-atherosclerosis syndrome 5

Assessment Approach

1. Screen for unexplained weight loss with poor appetite, particularly in:

   • Patients with diabetes 1
   • Cancer patients 1
   • Older hospitalized patients 3

2. Evaluate for inflammatory conditions:

   • Measure inflammatory biomarkers (CRP, albumin) in suspected cases 1
   • Consider infection as a cause of acute appetite changes 1

3. Review medication regimen:

   • Identify medications with known appetite-suppressing effects 2
   • Consider medication side effects, particularly psychotropic drugs 2, 6

4. Assess psychological factors:

   • Screen for depression, anxiety, and stress 1, 3, 4
   • Evaluate physical activity levels, particularly in older adults 3

5. Consider metabolic disorders:

   • Evaluate for diabetes and related metabolic disruptions 1
   • Assess for cancer-related metabolic changes 1

By systematically evaluating these potential causes, clinicians can identify the underlying factors contributing to poor appetite and develop appropriate treatment strategies to address them.