Undigested Fat In Stools

What Causes Undigested Fat In Stools?

Undigested fat in stools can have various causes, ranging in severity from 'minor' to 'critical'.  Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.

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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 undigested fat in stools, we could:

  • Research the topic
  • Find a doctor with the time
  • Use a diagnostic computer system.
The process is the same, whichever method is used.

Step 1: List all Possible Causes

We begin by identifying the disease conditions which have "undigested fat in stools" as a symptom.  Here are five possibilities:
  • Steatorrhea
  • Cystic Fibrosis
  • Short Bowel Syndrome
  • Liver Congestion
  • Heart Disease

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:
tetracycline use
heaviness of the legs
Caucasian ethnicity
severe calorie restriction
bags under eyes
moderate alcohol consumption
garlic intolerance
sickness caused by wine
diminished perspiration
tonsils/adenoids out before age 20
high uric acid level
calcium supplementation
... and more than 70 others

Step 3: Rule Out or Confirm each Possible Cause

A differential diagnosis of your symptoms and risk factors finds the likely cause of undigested fat in stools:
Cause Probability Status
Liver Congestion 94% Confirm
Steatorrhea 25% Unlikely
Cystic Fibrosis 2% Ruled out
Short Bowel Syndrome 1% Ruled out
Heart Disease 1% 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.

If you indicate irregular stools, The Analyst™ will ask further questions including this one:
Do you pass stools containing undigested fat? These stools might be yellow or pale in color, float, contain white specks, or leave an oily film on the toilet water.
Possible responses:
→ No / don't know
→ Occasionally
→ Often
Based on your response to this question, which may indicate undigested fat in stools, The Analyst™ will consider possibilities such as:
Coronary Disease / Heart Attack

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].


Stool fats (or fecal fats, or fecal lipids) are fats that are excreted in the feces.  When secretions from the pancreas and liver are adequate, emulsified dietary fats are almost completely absorbed in the small intestine.  When a malabsorption disorder or another cause disrupts this process, excretion of fat in the stool increases.

Steatorrhea also suggests the following possibilities:

Cystic Fibrosis

Most people with cystic fibrosis have difficulty absorbing dietary fat, which in turn leads to steatorrhea.  Cystic fibrosis interferes with the ability of the pancreas to secrete digestive enzymes: fat is normally broken down by lipase, a digestive enzyme that is produced and secreted by the pancreas.

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