I'm no expert but you might not be digesting the fats properly because you aren't producing enough bile or are lacking digestive enzymes or something. large amounts of medium chain triglycerides (like in coconut oil) does cause stomach upsets in some people but I'm not sure why. I also hear mixing animal fats can make your body respond in a funny way (probably an old wives tale). Maybe you need to gradually increase the amount of fat instead of having loads in one go?
"My mom made two dishes: Take it or Leave it." -- Stephen Wright, comedian