Question about eating in surplus I lift heavy 3x a week and do IF. I train early in the morning and usually don’t eat til noon.

I saw it was recommended to eat in a surplus on lifting days but was wondering if that’s still the go to if I always workout fasted. I’ve tried eating before working out but it’s just not for me. 

Up til now I’ve been eating maintenance on days I workout and deficit on rest days. 

I guess I just don’t really understand the principle behind eating in surplus if I’m not using that fuel to train on that day and wondering if it’s necessary. Any advice appreciated.