Definition

Unintentional weight loss is typically defined as a decrease in body weight of 5% or more within a 6 to 12-month period, without deliberate effort to lose weight[1][5]. This can be a sign of an underlying physical or mental disorder and is associated with increased mortality risk.

Etiology

Endocrine Disorders

• Hyperthyroidism: An overactive thyroid gland leads to increased metabolism, causing the body to burn calories at a faster rate. This can result in weight loss despite a normal or even increased appetite.
• Diabetes Mellitus (especially uncontrolled): In uncontrolled diabetes, the body can’t effectively use glucose for energy. As a result, it starts breaking down fat and muscle for fuel, leading to weight loss.
• Addison’s Disease: This condition affects the adrenal glands, leading to a deficiency in certain hormones. This can cause various symptoms, including weight loss, fatigue, and decreased appetite.

Gastrointestinal Disorders

• Celiac Disease: An autoimmune disorder where consuming gluten damages the small intestine, impairing nutrient absorption and leading to weight loss.
• Crohn’s Disease and Ulcerative Colitis: These inflammatory bowel diseases can cause inflammation in the digestive tract, leading to poor nutrient absorption, decreased appetite, and weight loss.
• Peptic Ulcers: Ulcers in the stomach or small intestine can cause pain, nausea, and vomiting, which can lead to decreased food intake and weight loss.

Cancer

• Various cancers: Unexplained weight loss is a common symptom of many types of cancer, particularly cancers of the digestive system (e.g., esophageal, stomach, pancreatic, colon). Cancer cells have a high metabolic rate, consuming a lot of energy and leading to weight loss.

Infections

• Tuberculosis (TB): This bacterial infection often affects the lungs but can also affect other parts of the body. It can cause weight loss, fever, and night sweats.
• HIV/AIDS: This viral infection weakens the immune system, making individuals susceptible to various infections and illnesses that can cause weight loss.

Mental Health Conditions

• Depression: Depression can significantly affect appetite and motivation to eat, leading to weight loss.
• Anxiety Disorders: Severe anxiety can also cause decreased appetite and digestive issues, contributing to weight loss.
• Eating Disorders: Conditions like anorexia nervosa and bulimia nervosa are characterized by disordered eating patterns and can lead to severe weight loss.

Other Conditions

• Heart Failure: In advanced heart failure, the body may not be able to effectively absorb nutrients, leading to weight loss and muscle wasting.
• Chronic Obstructive Pulmonary Disease (COPD): This lung condition can make breathing difficult, increasing energy expenditure and potentially leading to weight loss.
• Parkinson’s Disease: This neurological disorder can affect swallowing and appetite, contributing to weight loss.

Additional Causes

• Fungal infections: Often accompanied by fever, night sweats, fatigue, cough, and dyspnea[9].
• HIV/AIDS: Can present with fever, dyspnea, cough, lymphadenopathy, diarrhea, and candidiasis[9].
• Tuberculosis: Characterized by fever, night sweats, cough, and hemoptysis[9].

Teeth

• Poor dentition: May lead to difficulty eating and reduced food intake[5].
• Dysgeusia: Loss of taste can affect appetite and food enjoyment[9].

Psychogenic

• Depression: Characterized by sadness, fatigue, loss of sexual desire, sleep disturbance, and psychomotor retardation[9].
• Anorexia nervosa: Presents with inappropriate fear of weight gain in an emaciated individual, often with amenorrhea[9].

Intoxication

• Alcohol abuse: Can lead to malnutrition and liver problems[9].
• Drug addiction: Various substances can affect appetite and metabolism[2].

Medication

• Certain medications can cause weight loss as a side effect, including some psychotropic drugs, herbal products, and over-the-counter medications[1].

Findings in Clinical Examination

• Documented weight loss compared to previous records
• Changes in clothing size or fit
• Signs of underlying conditions (e.g., thyroid enlargement, abdominal masses)
• Nutritional deficiency signs
• Dental problems
• Skin changes (e.g., hyperpigmentation in Addison’s disease)
• Neurological symptoms (e.g., tremor in hyperthyroidism)

Diagnostic Approach

1. Comprehensive history and physical examination[4].
2. Basic laboratory tests:
   • Complete blood count
   • Basic metabolic panel
   • Liver function tests
   • Thyroid function tests
   • C-reactive protein and erythrocyte sedimentation rate
   • Fasting glucose
   • Urinalysis
   • Fecal occult blood test[5]
3. Imaging:
   • Chest radiography
   • Consider abdominal ultrasonography[5]
4. Additional tests based on clinical suspicion:
   • Endoscopy or colonoscopy for GI symptoms
   • HIV testing
   • Specific hormone level tests (e.g., cortisol for Addison’s disease)
   • Cancer screening appropriate for age and risk factors[5]
5. Follow-up and observation if initial evaluation is inconclusive[5].

Remember that the diagnostic approach should be tailored to each patient’s specific presentation and risk factors.