What I remember, I think the city was underground. The protagonist was a male teen, possibly with psychic powers.
I do remember a scene where the protagonist was mentally going on about zero calorie food when he was in a lift (Elevator). I also remember at the end of the book he had to change the shade of his skin.
He had a background of a gifted school or something, and also the main protagonist had a female friend from the same school. I think he worked at/near a bar. The lift scene thought process was brought on because fat people were in the lift with him. I think the cover had him on a flying/hovering machine.
I'm forty one and I read this in my teens. So nothing published after 1995.