# Why is fast food hard to digest? **URL:** \ **Category:** Factual Questions\ **Created:** [November 4, 2007, 10:43pm UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216 "2007-11-04T22:43:40Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![cainxinth](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@cainxinth](https://boards.straightdope.com/u/cainxinth)\ **Post date:** [November 4, 2007, 10:43pm UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/1 "2007-11-04T22:43:40Z")
I understand that McDonald’s, Domino’s, Taco Bell and the like is loaded with saturated fats, sodium, and sugars, which is why it can contribute to obesity, hypertension, and other negative health effects. But, why exactly is it so hard to digest. For a lot of people, myself included, the occasional fast food binge comes with all sorts of nasty digestive problems. What exactly is in a greasy pizza that my guts can’t deal with and why? ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [November 4, 2007, 10:53pm UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/2 "2007-11-04T22:53:26Z")
Well, the grease itself seems to be a pretty major contributor. Also, there’s probably no dietary fiber. Anecdotally, whenever I make a major change in my diet, such as switching to or away from fatty foods, my digestive tract protests. WAG: If you don’t eat lots of fatty foods normally, your body may not be producing enough bile to bind up all the fat you get in a fast food binge. ---
**Author:** ![cainxinth](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@cainxinth](https://boards.straightdope.com/u/cainxinth)\ **Post date:** [November 4, 2007, 11:29pm UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/3 "2007-11-04T23:29:54Z")
This is a weird follow up question, but if a person is in fact under-producing bile and some fat isn’t digested, and instead is excreted, does that mean technically I consumed less fat than the product contained? A gross but potentially beneficial side effect? ---
**Author:** ![robcaro](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@robcaro](https://boards.straightdope.com/u/robcaro)\ **Post date:** [November 5, 2007, 12:03am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/4 "2007-11-05T00:03:37Z")
I believe that fast foods do not have any fiber to assist in the throughput of digestion. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 5, 2007, 12:12am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/5 "2007-11-05T00:12:35Z")
[QUOTE=cainxinth] This is a weird follow up question, but if a person is in fact under-producing bile and some fat isn’t digested, and instead is excreted, does that mean technically I consumed less fat than the product contained? A gross but potentially beneficial side effect? [/QUOTE] What one often has with eating food laden with fats is such a high fat load that the body cannot produce enough lipase to digest it all. LOTS of fat calories get absorbed, but that which does not gets digested by the bacteria in the gut, where it is broken down into incredibly noxious, gassy compounds. This is called steatorrhea, and results in foul, frothy, floating feces which leave oil slicks on the toilet water surface. Hardly a beneficial side-effect. ---
**Author:** ![cainxinth](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@cainxinth](https://boards.straightdope.com/u/cainxinth)\ **Post date:** [November 5, 2007, 12:31am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/6 "2007-11-05T00:31:36Z")
[QUOTE=Qadgop the Mercotan] LOTS of fat calories get absorbed… [/QUOTE] How much is lots? 90% or more? ---
**Author:** ![cainxinth](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@cainxinth](https://boards.straightdope.com/u/cainxinth)\ **Post date:** [November 5, 2007, 12:45am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/7 "2007-11-05T00:45:42Z")
It occurred to me I should clarify why I’m asking this question. I’m not trying to figure out if I’ve stumbled upon a radical dieting program. I’m simply curious as to the extent of fat that goes undigested. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [November 5, 2007, 1:23am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/8 "2007-11-05T01:23:42Z")
[QUOTE=cainxinth] fat isn’t digested, and instead is excreted, does that mean technically I consumed less fat than the product contained? A gross but potentially beneficial side effect? [/QUOTE] Isn’t that the basic logic behind Olestra? ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [November 5, 2007, 2:04am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/9 "2007-11-05T02:04:14Z")
[QUOTE=t-bonham@scc.net] Isn’t that the basic logic behind Olestra? [/QUOTE] Heh. You almost said “anal leakage.” ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [November 5, 2007, 3:06am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/10 "2007-11-05T03:06:46Z")
**cainxinth** wondered what percent of food calories would still be absorbed even if the body’s ability to produce digestive enzymes such as lipase were overwhelmed. Although addressing a different question, [this study showed](http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=6190422&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum) that when some people take huge quantities of laxatives - enough to cause more than 5 litres of diarrhea :eek: - there is still almost 90% absorption of ingested food calories. ---
**Author:** ![WoodenTaco](https://avatars.discourse-cdn.com/v4/letter/w/45deac/32.png) [@WoodenTaco](https://boards.straightdope.com/u/WoodenTaco)\ **Post date:** [November 5, 2007, 3:22am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/11 "2007-11-05T03:22:01Z")
[QUOTE=Qadgop the Mercotan] What one often has with eating food laden with fats is such a high fat load that the body cannot produce enough lipase to digest it all. LOTS of fat calories get absorbed, but that which does not gets digested by the bacteria in the gut, where it is broken down into incredibly noxious, gassy compounds. This is called steatorrhea, and results in foul, frothy, floating feces which leave oil slicks on the toilet water surface. Hardly a beneficial side-effect. [/QUOTE] Thanks for all the imagery, doc. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [November 5, 2007, 5:03am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/12 "2007-11-05T05:03:41Z")
[QUOTE=Qadgop the Mercotan] What one often has with eating food laden with fats is such a high fat load that the body cannot produce enough lipase to digest it all. LOTS of fat calories get absorbed, but that which does not gets digested by the bacteria in the gut, where it is broken down into incredibly noxious, gassy compounds. This is called steatorrhea, and results in foul, frothy, floating feces which leave oil slicks on the toilet water surface. Hardly a beneficial side-effect. [/QUOTE] More fiber and Probiotics might help. But eating healthier choices, even at the Fast Food restaurant is best. Salads, baked potaties, and so forth. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [November 5, 2007, 5:14am UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/13 "2007-11-05T05:14:07Z")
[QUOTE=KarlGauss] **cainxinth** wondered what percent of food calories would still be absorbed even if the body’s ability to produce digestive enzymes such as lipase were overwhelmed. Although addressing a different question, [this study showed](http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=6190422&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum) that when some people take huge quantities of laxatives - enough to cause more than 5 litres of diarrhea :eek: - there is still almost 90% absorption of ingested food calories. [/QUOTE] Which is one reason why bulimics who abuse laxatives tend not to lose any significant weight at it. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [November 5, 2007, 3:07pm UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/14 "2007-11-05T15:07:34Z")
[QUOTE=KarlGauss] **cainxinth** wondered what percent of food calories would still be absorbed even if the body’s ability to produce digestive enzymes such as lipase were overwhelmed. Although addressing a different question, [this study showed](http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=6190422&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum) that when some people take huge quantities of laxatives - enough to cause more than 5 litres of diarrhea :eek: - there is still almost 90% absorption of ingested food calories. [/QUOTE] I wonder which poor lab technician got the 5-litres-of-diarrhoea detail. Suddenly my job seems not so bad. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [November 5, 2007, 3:26pm UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/15 "2007-11-05T15:26:58Z")
[QUOTE=WhyNot] Which is one reason why bulimics who abuse laxatives tend not to lose any significant weight at it. [/QUOTE] Indeed. The primary goal of the study was to clarify exactly that. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [November 5, 2007, 3:33pm UTC](https://boards.straightdope.com/t/why-is-fast-food-hard-to-digest/425216/16 "2007-11-05T15:33:25Z")
[QUOTE=Colophon] I wonder which poor lab technician got the 5-litres-of-diarrhoea detail. Suddenly my job seems not so bad. [/QUOTE] And this coming from somone with the words “pooh” and “colon” right in their user name.