Steatorrhea (or steatorrhoea) is the presence of excess fat in faeces. Stools may also float due to excess lipid, have an oily appearance and be especially foul-smelling. An oily anal leakage or some level of fecal incontinence may occur. There is increased fat excretion, which can be measured by determining the fecal fat level. The definition of how much fecal fat constitutes steatorrhea has not been standardized.
Possible biological causes can be lack of bile acids (due to liver damage, hypolipidemic drugs, or gallbladder removal (cholecystectomy)), defects in pancreatic enzymes, defective mucosal cells, certain medicines that block fat absorption, or indigestible or excess oil/fat in diet. The absence of bile acids will cause the feces to turn gray or pale. Another cause of steatorrhea is due to the adverse effect of octreotide or lanreotide, which are analogs of somatostatin, used clinically to treat acromegaly.
Orlistat (also known by trade names Xenical and Alli) is a diet pill that works by blocking the enzymes that digest fat. As a result, some fat cannot be absorbed from the gut and is excreted in the faeces instead of being metabolically digested, sometimes causing oily anal leakage. VYTORIN® (ezetimibe/simvastatin) tablets can cause Steatorrhea in some people.
There are anecdotal reports on the internet describing oily droplets in feces after eating large amounts of cashews or other whole nuts. They in agreement with studies showing that stool lipids are greatest when whole nuts are eaten, compared to their nut butters, oils or flour  and that lipids from whole nuts are significantly less well absorbed.
Consuming jojoba oil has been documented to cause steatorrhea and anal leakage because it is indigestible.
Consuming escolar and oilfish (sometimes called butterfish) will often cause steatorrhea, also referred to as Gempylotoxism or Gempylid Fish Poisoning or keriorrhea. The fish is commonly used in party catering due to its delicate flavor and because it is cheap and readily available.
The fat substitute Olestra, used to reduce digestible fat in some foods, was reported to cause leakage in some consumers during the test-marketing phase. As a result, the product was reformulated before general release to a hydrogenated form that is not liquid at physiologic temperature. The U.S. Food and Drug Administration warning indicated excessive consumption of Olestra could result in "loose stools"; however, this warning has not been required since 2003.
^Hasosah, MY; Shesha, SJ; Sukkar, GA; Bassuni, WY (2010). "Rickets and dysmorphic findings in a child with abetalipoproteinemia". Saudi medical journal31 (10): 1169–71. PMID20953537.
^ abSquires, Sally (2006-01-24). "Weighing a Pill For Weight Loss". Washington Post. Retrieved 2007-07-06. "While the Food and Drug Administration (FDA) still must approve the switch, the agency often follows the advice of its experts. If it does, Orlistat (xenical) -- currently sold only by prescription -- could be available over-the-counter (OTC) later this year. But it's important to know that the weight loss that's typical for users of the drug -- 5 to 10 percent of total weight -- will be less than many dieters expect. And many consumers may be put off by the drug's significant gastrointestinal side effects, including flatulence, diarrhea and anal leakage."
^ ab"Frito-Lay Study: Olestra Causes "Anal Oil Leakage"". Center for Science in the Public Interest. February 13, 1997. Retrieved 2007-07-07. "The Frito-Lay report states: "The anal oil leakage symptoms were observed in this study (3 to 9% incidence range above background), as well as other changes in elimination. ... Underwear spotting was statistically significant in one of two low level consumer groups at a 5% incidence above background." Despite those problems, the authors of the report concluded that olestra-containing snacks "should have a high potential for acceptance in the marketplace.""
^ ab"The Word Is 'Leakage'. Accidents may happen with a new OTC diet drug.". Newsweek. June 25, 2007. Archived from the original on 2007-06-18. Retrieved 2007-06-21. "GlaxoSmithKline has a tip for people who decide to try Alli, the over-the-counter weight-loss drug it is launching with a multimillion-dollar advertising blitz—keep an extra pair of pants handy. That's because Alli, a lower-dose version of the prescription drug Xenical, could (cue the late-night talk-show hosts) make you soil your pants. But while Alli's most troublesome side effect, anal leakage, is sure to be good for a few laughs, millions of people who are desperate to take off weight may still decide the threat of an accident is worth it."