I used to only be able to eat one small thing per day (like half of a small chicken sandwich), then after dinner, until morning next day, I would vomit bright yellow, orange, and toxic green stuff. Generally it would come from both ends.
I spent the night by the toilet, curled up on the floor.
I think the yellow and orange was acid, and the neon green was bile.
The problem was gallbladder (I only had one tiny gallstone!), but after some time it also started affecting the liver and the and pancreas. The doctors told me to eat no fat at all, which made me really angry since I'd already been doing that for YEARS and only got worse and worse! The doctors wanted me to remove the gallbladder.
One time I ended up in the emergency. And the next day, my mom visited me (she lives abroad). She saw how sick I was and decided to stay to look after me.
I was very weak so I just ate what she cooked for me. I didn't have any food in the house anymore, because I wasn't working and had no money.
So for one week, I had no choice on what I ate.
She cooked me things like BBQ pulled pork (made with lots of lard), egg yolks cooked in butter, sardines... and vegetables like yams, carrots, and cabbage. And cheese. Lots of good quality fatty cheeses.
Since the first day she was here, I didn't vomit or have pain anymore. No diarrhea either.
And I wasn't tired, I was strangely bright and energetic. I wanted to go for walks and clean the house!
I was scared I would get sick again.
But I was so shocked that I was better suddenly, so I searched google. I found information that said it's by eating low-fat and eating grains that you get gallbladder problems.
I didn't believe it. But I tried eating low fat and grains, and yep, I got sick again! So as long as I don't eat grains, nuts, and legumes, I don't have any pain, diarrhea or vomiting.
And I still have my gallbladder!
Edit: why grains, legumes, and nuts? (I didn't mention it, but also seeds).
Think about it, these are seeds. They want to be planted to grow into plants. They don't want to be digested. They have protections against that: phytic acid.
http://www.westonaprice.org/food-features/living-with-phytic-acid
I can now eat things like real bread (sourdough), and properly prepared beans and nuts, but I don't eat them more than once per week or I start getting bloated and might feel pain. And they need to be traditionally prepared, not commercial.