hi Maryan ,Acne
may occur beside face at back ,upper chest ,upper part of arms some times at hip area also, take care of it by frequent washing of affected parts ,don't apply oily creams and oil etc. consult your dermatologist
,he/she will prescribe you some ointments
,that would be very effective in your case .
so don't get dis hearted as acne has no relation with food ,It is a common problem in your age .
Dr Prakash Roy