Almost any small intestinal disease (including Crohn's) may affect fat absorption. Low-fat diet can greatly improve your diarrhea. You can also have a no-dairy diet trial. When small intestinal mucosa is injured, less enzyme lactase (which digests lactose - milk sugar) is produced and causes diarrhea after milk products. I find abdominal organs and diseases easy to understand, I can virtually see all abdominal processes. I also noticed a great influence of the diet on my bowel, and I've seen a lot of gastric issues in my family and in others. Non-solved abdominal issues can really affect your life. Anyone can do a lot to solve this problems, and abdominal treatment is also often successful.