What Causes Weight Loss?
Weight loss can have various causes, ranging in severity from 'minor' to 'generally fatal'. Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.
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- understand what's happening to your body
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Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms. In order to diagnose weight loss, we could:
- Research the topic
- Find a doctor with the time
- Use a diagnostic computer system.
Step 1: List all Possible Causes
We begin by identifying the disease conditions which have "weight loss" as a symptom. Here are eight of many possibilities (more below):
- Vitamin B12 Need
- Cancer In General
- Anorexia/Starvation Tendency
- Hepatitis
- Short Bowel Syndrome
- Lupus (SLE)
- Pulmonary Fibrosis
- Underconsumption
Step 2: Build a Symptom Checklist
We then identify all possible symptoms and risk factors of each possible cause, and check the ones that apply:
being an unsocial person
broad-spectrum antibiotic use
major inflamed cuticles
having had a small bowel resection
dark urine color
being easily irritated
chronic dry cough
loss of appetite
sleeping more than necessary
unexplained fevers that hit hard
anorexia
major joint pain/swelling/stiffness
being an unsocial person broad-spectrum antibiotic use major inflamed cuticles having had a small bowel resection dark urine color being easily irritated chronic dry cough loss of appetite sleeping more than necessary unexplained fevers that hit hard anorexia major joint pain/swelling/stiffness... and more than 100 others
Step 3: Rule Out or Confirm each Possible Cause
A differential diagnosis of your symptoms and risk factors finds the likely cause of weight loss:
| Cause | Probability | Status |
|---|---|---|
| Cancer In General | 93% | Confirm |
| Hepatitis | 29% | Unlikely |
| Underconsumption | 12% | Unlikely |
| Pulmonary Fibrosis | 3% | Ruled out |
| Vitamin B12 Need | 2% | Ruled out |
| Lupus (SLE) | 0% | Ruled out |
| Anorexia/Starvation Tendency | 0% | Ruled out |
| Short Bowel Syndrome | 0% | Ruled out |
* This is a simple example to illustrate the process
Arriving at a Correct Diagnosis
The Analyst™ is our online diagnosis tool that learns all about you through a straightforward process of multi-level questioning, providing diagnosis at the end.
|
Has your weight decreased significantly for unknown reasons in the past year?
Possible responses:
→ Don't know / not applicable→ No / minimal change → 5% to 10% / moderate weight loss → 11% to 20% / major weight loss → Over 20% / very great weight loss |
Carcinoid Cancer
Weight loss can occur in carcinoid syndrome, as in most cancers, and the presence of diarrhea may contribute to further losses.
Coronary Disease / Heart Attack
Weight loss is a common finding among individuals with chronic heart failure. It is evident that malabsorption of fats is related to heart failure. In one study, subjects with heart disease had 10 times more fat in their stool than heart-healthy individuals. This means those with heart disease weren't absorbing their fats [Am J Cardiology 5: p.295, 1960]. Yet heart patients are typically placed on low-fat diets! These individuals were leaner, but not healthier.
Diabetes Type II
Weight loss can indicate uncontrolled diabetes, while weight gain suggests an increased risk of getting it.
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Last updated: Jan 15, 2026