Heat, humidity, activity, time of day, amount eaten, what you ate at other times, hydration, illness, stress, the phase of the moon, what color shirt you are wearing, etc. Sorry if that was a bit silly but really there are so many factors that come into it and so many hormones at play that there is really no way of telling. It could be that if it is more carby food than your body is used to, two days in a row is too much. I have some wraps that I found that are quite high fiber, I found that I could have one and it was fine. The other day I got lazy and had one for lunch and then one for dinner. I woke up the next day with a fasting of almost 8 and up 4 pounds. I guess I went over some line that my body has drawn in the sand. Live and learn, I won't do it again.