Is fat neccessary

Hi all, I am starting out on this recovery program having dabbled before but never with the correct frame of mind. However, this time around I am approaching it from a different place and am looking forward to doing it whereas before I dreaded it.
So obviously I haven't yet reached the potato at bed time phase.
However I want to plan as I don’t want to be unprepared in my mind.
I don’t think a potato will be possible so I was wondering about a whole grain, sugar free breakfast cereal or maybe Ryvita or oatcake.
Also along with this question, as I noticed the potato comes with butter, is it strictly necessary to have fat with this evening meal.
Answers with reasons would be very much appreciated.