It can be hard to tell.But the question becomes if you eat food A at 8 am the next day food B at noon and food C at five, when do you have the symptoms.With that timing any of them can be it.If C was really fatty, I'd go for C.If A is something that draws extra water into the stool, or might make gas when it hit the colon, I'd go with A.So you can look at things like that.K.