food after workout

Greetings
just a question or 2 about pre/post workout food
typically i do chest/shoulder and/or triceps on saturday or sunday
monday - 30-45mins high intensity interval training (HIIT)
tuesday - back/biceps with only 20 mins aerobic
wednesday - if i dont do weights tuesday i do above
thursday - legs and aerobic
friday day off

this isnt set in stone and i tend to have probably another day off sometimes - been doing it for about 1.5 months. Scales are different at home than at the gym and have dropped about 2-3cm from waist (currently 40 inches, 101cm).
I dont have a weight in mind, other than training to get in better shape, i will know when i am happy.
BIg question is pre workout and post work out food, especially when Ive only done aerobic.
Any ideas will be great
CHeers
Justin