How unhealthy is pizza? having pizza for lunch once a week is bad?

Occasional is fine: Pizza is fine if one doesn't eat too much. Twice a week is fine. Because pizza has cheese (usually half fat, half protein) it has plenty of fat. The salt usually is from the pepperoni or sausage. So, to be healthy, one can eat salad with no cheese and little dressing, plus drink water or sugarless tea, when eating pizza. Lower fat, lower salt pizzas: Hawaiian, veggie, or chicken with light cheese.

Leaner pizza.: Just about any food can be made a bit leaner. As far as pizza, try with light or even no cheese. Try vegetable toppings rather than sausage or pepperoni. Thin crust rather than deep dish or Sicilian. And don't eat the whole thing - maybe two slices only. This would cut the calories a lot and sodium a bit. Once weekly for lunch would be fine.