I always eat a lot of meat when I am visiting that place.
I think it means "while I am visiting that place I am always eating a lot of meat".
However, I think it can mean
I always eat a lot of meat when I am going to visit that place.
It's a different meaning. The bottom line is this:
when I am doing can mean:
a) while I am doing
b) when I am going to do
Do you agree?