I got -500 to ~600 (it varies) food demand from almost the beginning of the game.
I started my race with double food consumption, but that doesn't trigger it AFAIK, and also received a weird proposition from one of the AIs, with only the "declare war on failure" clause, no conditions, so I accepted for kicks, and now I can't get read of that agreement
Don't know what triggers the -500 food in galactic bank and because of it I have to have farms on all planets from now on
EDIT: also I've started the race with the debt trait that halves all bank exports for the first 20 minutes
EDIT 2: after a while it went away on it's own , although it was fluctuating wildly between 470 and 680 food consumption!? Perhaps it's the weird clause treaties I get form the AI, and the food clause was invisible... I won't accept any such bugged treaties in the future
EDIT 3: surely it's the bugged treaty, I got another one from the AI from which I accepted the bugged treaty, and although the new treaty had a clause declare war upon refusal, war was not declared