Curious, pizza seems really healthy to me: Cheese, tomatoes, veggies, maybe a tiny bit of meat, the dough isn't really worse than normal bread (get whole wheat dough!)
It's unhealthy and will make you fat - the dough is normally white bread which is awful for you, wheat bread has a slightly lower glycemic index but more calories and it is still bad for you. Cheese which is incredibly calorie dense and really fattening, tomato paste is basically water. Stay away!
Healthy is perhaps the ~wrong word. You're right in what you say. For example, if you are starving in the sense of being calorically depreived, (american) pizza is quick, efficient, and cost effective nutrition. The problem with pizza is that most people that eat it, are not like the above example. In that case, they need to me more concerned about the effect of the pizza on their sense of satiation and metabolism. That is in addition to stopping eating pizza. While the latter are grey areas, the slope is slippery toward indulgence. Which is simply eating to get the rush/endorphins of eating such a calorically rich and diverse foodstuff. Which sucks if you are a sedentary person, but is NBD if you are michael phelps. =D
