5:2 Diet Stomach Probs

You cannot really know if it was walnuts. Unless this has happened before.
Could the walnuts gave the walnuts gone off ?

I can’t see that the 5:2 should cause this.
I haven’t seen any other comments on the subject that mentioned diahorrea before.
Perhaps, as Monica says, just coincidence.

I think it may be your GI tract just getting into action after an unaccustomed fast. The cramps may be normal peristalsis kicking into action thinking a more substantial breakfast was on the way. I sometimes get it

Peristalsis is the normal mechanism for moving (squeezing) bowel contents along and nothing to be alarmed about.

Try a weekend fast day and see what happens.

I have been following this way of eating for nearly 5 years now and have never had the problems you mention. It may just be coincidence.

I eat a wide range of foods on fast days, although mainly vegetables.