Why Does Eating Fat Make Me Sick?

I asked this question to various doctors while my symptoms were being investigated and I never got a clear reply. So if you are experiencing pain, sickness, diarrhoea or even just foul breath and eggy burps after eating fatty food then hopefully I can help you to understand why.

Firstly how is fat digestion supposed to work? The majority of fat digestion occurs in the small intestine. When the fat reaches the start of the small intestine (duodenum) it triggers the release of hormones which in turn initiate the release of enzymes from the pancreas and bile from the liver (via the gall bladder and bile duct, see here for an excellent diagram of the digestive system). The healthy stomach is very acidic mainly to assist in protein digestion and to break down or damage any pathogens (germs) that may have found their way into the stomach. However our digestive enzymes are proteins too so they do not work as well in an acidic environment. One function of bile, along with sodium bicarbonate released from the pancreas, is to restore an almost neutral pH to the bowel so the digestive enzymes can function properly. Bile is also essential to fat digestion by making the fat molecules water soluble (emulsification) which makes the digestive enzymes job much easier. The most important enzyme for fat digestion is pancreatic lipase, it completes the digestion process and allows the small intestine wall to absorb the fat molecules.

So this is how the fully functional fat digestion process works but why and how does this process end up causing pain and sickness in some people? If you have had all the tests and scans showing no ulcers, inflammation, gallstones, pancreatitis or other disease then the fault will possibly lie with irritable bowel syndrome (IBS).

The main symptoms of IBS are caused by erratic bowel spasms. If one or more of these spasms occurs in the duodenum it can result in the stomach not being able to drain properly (sometimes known as gastroparesis) leaving an uncomfortable full sensation, bloating, bad breath, nausea, stomach cramps and feelings of ‘indigestion’ (dyspepsia). I have found eating smaller meals more frequently helps with all of these symptoms and low dose (10mg) amitriptyline helps with the discomfort and pain.

Why are these symptoms worse when fat is present? This could be the result of ‘bile reflux’. Bile is only released in the presence of fat in the duodenum and bowel spasms may push this bile into stomach. Bile is not normally present in the stomach so this upsets the normal digestive process. There are some reports that bile can damage the stomach lining resulting in symptoms of gastroenteritis (gastritis) or worse lasting damage but I do not believe these have been scientifically verified and should not be something to worry about. Bile acid sequestrant medication can help with these symptoms. Bile acid sequestrants include: Cholestyramine (Questran) , Colesevelam (Cholestagel in Europe, Welchol in the USA) and Colestipol (Colestid, Colestipid).

The worst symptoms I get after eating fatty foods are extreme stomach pain (usually occurring in the night or very early morning), vomiting and diarrhoea match closely those of biliary colic. Biliary colic is the pain resulting from gallstones blocking one or more of the ducts leading from or to the gallbladder causing it to distend. So it is possible that the bowel spasms somehow prevent draining of bile from the gallbladder into duodenum causing the gallbladder to painfully distend. In a similar way bowel spasms could mimic pancreatitis as bowel spasms could prevent draining of the pancreas via the pancreatic duct into the duodenum. Both amitriptyline and bile acid sequestrants help to control the diarrhoea but the best treatment I have found to prevent these extreme episodes is to eat a very low fat diet. I have not found any medication that helps, even powerful painkillers do not control the pain it is simply a matter of waiting it out. Unfortunately there is no ‘cheat day’ on this diet even one sneaky chocolate bar would result in a really bad night. For more information on my diet see here.


10 thoughts on “Why Does Eating Fat Make Me Sick?

  1. […] for ‘why does eating out make me ill’ and I really hope they found some help from my blog. Unfortunately eating out is almost impossible when you have to be careful about how much fat you […]

  2. Boris says:

    You’re wrong about the fact that Giardia can only be contracted in those locations. Giardia is endemic even in the United States! Do a google search on giardiasis.

    I’m currently being treated for it and I haven’t been to those places.

    • Victoria says:

      Hello there,
      I too am suffering with this problem.
      It began for me in august 2010 and I still have no resolution but I would have to say I disbelieve the IBS theory. I have many friends who suffer with IBS and they have came and seen me in hospital and cannot believe there eyes.
      It started when I was pregnant, the doctors too went down the route of gall stones, (or sludge) so I had that removed. My symptoms are more severe, when I have these episodes it does start either late at night or very early in the morning, the pain is like nothing I have ever experienced. I end up collapsed around the toilet or in the bed with a bowl, vomiting profusely like something from the exorcist. This episodes can last from 1 day to two weeks was my longest and I was hospitalised. Id say in the past two years I have been in a and e about 15 times. Morphine injected straight to the vein is the only thing that has evver got rid of the pain. Amtriptyline helps with the normal every day pains but the pain builds up and gets worse when I know Im going to have an attack and then nothing, even mst tablets work. The pain has spread to my lower back, some days i can barely walk. The only correlation is my constipation. I have now been referred to Prof Aziz at Barts hosptial and they believe that because i have an enlarged rectum and functional rectocele that there is no outlet for the waste, resulting in a build up of bad bacteria which results in these episodes. Ive had a camera in my sstomach which showed gastritus and I was also treated for h pylori bacteria too. I am currently at my wits end. Im under a dietician and have tried eliminating fat, dairy, wheat etc nothing makes a difference.
      . Im now having tests on my kidneys as they showed a problem on an mri scan and i have white blood cells in my urine. The only other thing I can think of is that my blood sugar always sky rockets when these episodes occur.I just wanted to share my story its also nice to find another person who seems to be going through the same thing.

      • suzymacd says:

        Thanks for your comment Victoria. I agree with you that your symptoms do not appear to be caused by IBS. I hope that when your rectocele is repaired this will solve your problems. I’ve read that eating sugars can exacerbate bacterial blooms in the gut – have you tried cutting out sugar? It’s possible encouraging the good bacteria with probiotics could help as well. I’m sure you already know about drinking plenty and not eating late. Out of interest following Boris’ comment have you been tested for Giardasis at any point in your treatment? Do you know if your lower back pain is musculoskeletal, possibly caused by your excessive vomiting? I’ve also recently been treated by a physiotherapist for a bad back and I know of someone else with similar GI symptoms who has also developed osteoarthritis in her lower spine. Hopefully your kidney problems are a simply treatable infection, which may also be contributing to your back pain. I really hope you find some relief from all of your symptoms soon.

    • suzymacd says:

      Thanks for your comment Boris. I had no idea Giardiasis was so prevalent in the US. I live in the UK where it isn’t so widespread and isn’t routinely tested for, perhaps it should be considering our close ties with our friends over the pond! I hope you are feeling better.

  3. Hebrides says:

    Hey guys…
    I went to Peru in 2003 and contracted Giardiasis. I was ill to the point that I was treated in Intensive Care. Fatty foods made me horrendously ill throughout the illness. If you dont mind details…. When I vomited, I would only bring up the fat that I had eaten. I also couldn’t digest difficult veggies like broccoli and green beans.
    I was treated with IV Antibiotics (Metronidazole and Ciprofloxacin) followed by a course of oral antibiotics.
    Even now, 9 years later, I get a flare up of the disease. In fact i am currently sitting up in bed having been ill all night after eating sausages.
    The symptoms are horrible indigestion, eggy burps, fevers and vomiting with occasional diarrhoea.

  4. Missy says:

    I too suffer from IBS & I too have trouble with digesting fats, all my life.
    Very long story short, Digestive enzymes are useless in helping to digest fat.

    Well, during a major attack last week & again researching the net for something new, I stumbled upon Digest-Aid Bile Salts (which is Ox-Bile). Boy did that do the trick. I very seldomly has stinky poo, but this release was the nastiest stench imagineable. I literally had to air the whole place out. I had a few more stinky released like that for the next few days and finally things settled down. I make sure I take one tablet WITH each meal that contains any fat.

    This product is dirt cheap too. Unlike other digestive enzymes which usually cost around the $20. mark, this was just under $8.00 and the best part is that it worked for me. Not to much info on the net about
    ox bile salts tho. I’m not sure if I am allowed to mention the brand name, if no, then please remove it. It’s made by Trophic Canada.

    Another thing that works great & I posted it a few years ago on the IBS forum, is to drink a small glass of raw potato juice 3 times a day on an empty stomach. Yep, you read that right, raw potato juice. Juice only what you will drink immediately. Stir the juice bcos starch settles and drink it quickly, all in one shot. Do not sip it. It kills the bad bacteria. You should see results within 3 days. I guess it takes that long for the good bacteria to flourish into an army that kills the bad guys.

    DO NOT peel the potato, just wash the skin real well.

    Back when I first posted this on the forum, there was hardly any info about the health benefits of raw potato juice and stomach/intestinal treatments. Today, there is plenty.

    Here’s a quote from one site:
    “Raw potato juice stimulates the digestive system, acts as a natural anti-inflammatory and is an alkaline food that may help restore the body’s optimum pH balance. The juice has also been used to treat stomach ulcers and liver disorders. Drinking raw potato juice cleanses the liver and prevents and relieves constipation. Because raw potato juice can speed up digestion and replenish “friendly” bacteria in the colon, it may aid in weight loss.”


    Do some google research for raw potato juice health benefits; raw potato juice treatment for IBS; raw potato juice kills bacteria.

    I hope my sharing these two tips helps someone. Good Luck 🙂

    FYI: Your comments window seems to have a problem. When I reach the end of the sentence and hit the return key, the text does not want to type OR it does type and the space bar won’t work & the cursor disappears. No, it’s not on my end, I checked.

  5. yolanda says:

    I geus I got to eat a low fat diet coz greasy foods are not working 4me

  6. […] properly. I have found that my symptoms are worst if I eat food that contains too much fat. In a previous post I discussed how eating fatty foods could cause biliary colic type symptoms due to irregular spasms […]

  7. […] found out so much more about what could be causing my symptoms (fat intolerance, eggy burps) over the last year. I’ve had a few theories, tried out a few different […]

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