What Is a Fecal Fat Test?
A fecal fat test measures the amount of fat in your feces or
stool. The concentration of fat in your stool can tell doctors how much fat
your body absorbs during digestion. Changes in stool consistency and odor can
indicate that your body isn’t absorbing as much as it should.
Fecal fat testing usually spans 24 hours, but it can
sometimes last for three days. During the testing period, you’ll need to
collect each stool sample with a special testing kit. Your local laboratory
will provide you with the testing kit and specific instructions about usage.
Some fecal test kits require you to collect the samples with plastic wrap.
Others include special toilet paper or plastic cups.
Purposes of Fecal Fat Testing
Fecal fat testing might be performed if your doctor suspects
that your digestive system isn’t functioning correctly. In a normal person, the
absorption of fat is based on a variety of factors:
production in the gallbladder or liver, if your gallbladder was removed
of digestive enzymes in the pancreas
functioning of the intestines
If any of these organs are not working properly, your body might
not be able to absorb as much fat as you need to remain healthy and nourished.
Decreased absorption of fat can be a sign of many different illnesses,
disease: damage to the intestinal
lining caused by an intolerance to gluten
disease: an autoimmune inflammatory
bowel disease affecting the entire digestive tract
fibrosis: a genetic disease resulting
in thick mucus secretions in the lungs and digestive tract
- pancreatitis: inflammation of the pancreas
- cancer: tumors in the pancreas or
People who have decreased absorption of fat often notice
changes in their bowel habits. This is because the fat that is not digested is
excreted in the feces. You might notice your stool is looser, almost
diarrhea-like in consistency. Stool with a high fat content also emits a
fouler-than-normal odor and is likely to float.
Preparing for Fecal Fat Testing
Everyone who undergoes fecal fat testing is required to
follow a high-fat diet for three days prior to the test. This allows for
accurate measurement of the fat concentration in the stool. You will be asked
to eat 100 grams of fat each day for three days before taking the fecal fat
test. This is not as difficult as one might think: Two cups of whole milk, for example,
contain 20 grams of fat, and 8 ounces of lean meat contain approximately 24
grams of fat.
Your doctor or dietitian may help you determine how to eat
the required fat each day. You might be given a list of suggested foods to help
you plan your meals. Whole milk, full-fat yogurt, and cheese can boost your fat
intake. Beef, eggs, peanut butter, nuts, and baked goods are also good sources
of fat. Reading the nutrition labels of the foods in your pantry gives you an
idea of how much fat you consume in each meal or snack. If you tend to eat more
than 100 grams of fat each day, the dietitian will teach you how to cut fat out
of your diet and make healthier choices.
After following the high-fat diet for three days, you’ll
return to a normal diet and begin the stool collection process. Have the
collection kit ready at home for the first day of testing.
Fecal Fat Testing Procedure
You need to collect stool each time you have a bowel
movement during your testing period. You might be given a plastic “hat” to
place over the toilet bowl, or be directed to loosely cover the bowl with
plastic wrap. Urinate before you place the hat or plastic over the toilet bowl.
Urine, water, and regular toilet paper can contaminate your sample and render
the test results inaccurate.
After the collection apparatus is in place, collect your
stool sample. You may be given additional tools, like a wooden or plastic
scoop, to transfer the sample into a special container. Cover the container
tightly and place either in the refrigerator, freezer, or in a separate cooler
that is insulated and filled with ice. Repeat the process each time you have a
bowel movement during the 24- or 72-hour testing period.
To carry out fecal fat testing in children, line the diaper
of babies and toddlers with plastic wrap. Try to place the plastic in the back
portion of the diaper to prevent the mixing of feces and urine.
When you have completed the fecal fat testing, write your (or
child’s) name, date, and time on the container. Return the sample container to
Interpreting the Results of Fecal Fat Testing
The normal range for fecal fat testing is 7 grams over a
24-hour period. Normal results for a 72-hour test would be 21 grams. Your
doctor will review results that are lower than normal. You might undergo
further testing based on your medical history and symptoms, to determine why
your fecal fat concentration is low.